Display device with overlapped flexible substrates for displaying a wide color gamut image

ABSTRACT

A display panel includes a plurality of light-emitting elements. Light emitted from a first light-emitting element has a CIE 1931 chromaticity coordinate x of greater than 0.680 and less than or equal to 0.720 and a CIE 1931 chromaticity coordinate y of greater than or equal to 0.260 and less than or equal to 0.320. Light emitted from a second light-emitting element has a CIE 1931 chromaticity coordinate x of greater than or equal to 0.130 and less than or equal to 0.250 and a CIE 1931 chromaticity coordinate y of greater than 0.710 and less than or equal to 0.810. Light emitted from a third light-emitting element has a CIE 1931 chromaticity coordinate x of greater than or equal to 0.120 and less than or equal to 0.170 and a CIE 1931 chromaticity coordinate y of greater than or equal to 0.020 and less than 0.060.

TECHNICAL FIELD

One embodiment of the present invention relates to a display device, anelectronic device, and a manufacturing method thereof.

Note that one embodiment of the present invention is not limited to theabove technical field. Examples of the technical field of one embodimentof the present invention include a semiconductor device, a displaydevice, a light-emitting device, an electronic device, a lightingdevice, an input device (e.g., a touch sensor), an input-output device(e.g., a touch panel), a driving method thereof, and a manufacturingmethod thereof.

BACKGROUND ART

In recent years, larger display devices have been required. Examples ofuses for a large display device include a television device for home use(also referred to as a TV or a television receiver), digital signage,and a public information display (PID). A larger display region of adisplay device can provide more information at a time. In addition, alarger display region attracts more attention, so that the effectivenessof the advertisement is expected to be increased, for example.

Light-emitting elements utilizing electroluminescence (also referred toas EL elements) have features such as ease of thinning and lightening,high-speed response to an input signal, and driving with adirect-current low voltage source; thus, application of the EL elementsto display devices has been proposed. For example, Patent Document 1discloses a flexible light-emitting device including an organic ELelement.

REFERENCE Patent Document

[Patent Document 1] Japanese Published Patent Application No.2014-197522

DISCLOSURE OF INVENTION

An object of one embodiment of the present invention is to increase thesize of a display device. Another object of one embodiment of thepresent invention is to provide a display device including a widedisplay region in which a seam is less likely to be noticed. Anotherobject of one embodiment of the present invention is to provide adisplay device that can display an image with a wide color gamut.Another object of one embodiment of the present invention is to suppressdisplay unevenness or luminance unevenness of a display device. Anotherobject of one embodiment of the present invention is to reduce thethickness or weight of a display device. Another object of oneembodiment of the present invention is to provide a display device thatcan display an image along a curved surface. Another object of oneembodiment of the present invention is to provide a highly browsabledisplay device. Another object of one embodiment of the presentinvention is to provide a novel display device.

Note that the description of these objects does not preclude theexistence of other objects. In one embodiment of the present invention,there is no need to achieve all the objects. Other objects can bederived from the description of the specification, the drawings, and theclaims.

A display device of one embodiment of the present invention includes afirst display panel and a second display panel. The first display panelincludes a first display region. The second display panel includes asecond display region and a region transmitting visible light. Thesecond display region is adjacent to the region transmitting visiblelight. The first display region includes a portion overlapping with theregion transmitting visible light. The first display panel includes afirst light-emitting element, a second light-emitting element, and athird light-emitting element. Light emitted from the firstlight-emitting element has a CIE 1931 chromaticity coordinate x ofgreater than 0.680 and less than or equal to 0.720 and a CIE 1931chromaticity coordinate y of greater than or equal to 0.260 and lessthan or equal to 0.320. Light emitted from the second light-emittingelement has a CIE 1931 chromaticity coordinate x of greater than orequal to 0.130 and less than or equal to 0.250 and a CIE 1931chromaticity coordinate y of greater than 0.710 and less than or equalto 0.810. Light emitted from the third light-emitting element has a CIE1931 chromaticity coordinate x of greater than or equal to 0.120 andless than or equal to 0.170 and a CIE 1931 chromaticity coordinate y ofgreater than or equal to 0.020 and less than 0.060. Alternatively, thefirst light-emitting element emits light that has a CIE 1931chromaticity coordinate x of greater than 0.680 and less than or equalto 0.720 and a CIE 1931 chromaticity coordinate y of greater than orequal to 0.260 and less than or equal to 0.320. The secondlight-emitting element emits light that has a CIE 1931 chromaticitycoordinate x of greater than or equal to 0.130 and less than or equal to0.250 and a CIE 1931 chromaticity coordinate y of greater than 0.710 andless than or equal to 0.810. The third light-emitting element emitslight that has a CIE 1931 chromaticity coordinate x of greater than orequal to 0.120 and less than or equal to 0.170 and a CIE 1931chromaticity coordinate y of greater than or equal to 0.020 and lessthan 0.060.

A display device of one embodiment of the present invention includes afirst display panel and a second display panel. The first display panelincludes a first display region. The second display panel includes asecond display region and a region transmitting visible light. Thesecond display region is adjacent to the region transmitting visiblelight. The first display region includes a portion overlapping with theregion transmitting visible light. The first display panel includes afirst light-emitting element, a second light-emitting element, a thirdlight-emitting element, a first coloring layer, a second coloring layer,and a third coloring layer. Light obtained from the first light-emittingelement through the first coloring layer has a CIE 1931 chromaticitycoordinate x of greater than 0.680 and less than or equal to 0.720 and aCIE 1931 chromaticity coordinate y of greater than or equal to 0.260 andless than or equal to 0.320. Light obtained from the secondlight-emitting element through the second coloring layer has a CIE 1931chromaticity coordinate x of greater than or equal to 0.130 and lessthan or equal to 0.250 and a CIE 1931 chromaticity coordinate y ofgreater than 0.710 and less than or equal to 0.810. Light obtained fromthe third light-emitting element through the third coloring layer has aCIE 1931 chromaticity coordinate x of greater than or equal to 0.120 andless than or equal to 0.170 and a CIE 1931 chromaticity coordinate y ofgreater than or equal to 0.020 and less than 0.060. Note that colorfilters or the like can be used as the coloring layers.

The first coloring layer preferably has a 600-nm light transmittance ofless than or equal to 60% and a 650-nm light transmittance of greaterthan or equal to 70%. The second coloring layer preferably has a 480-nmlight transmittance of less than or equal to 60%, a 580-nm lighttransmittance of less than or equal to 60%, and a 530-nm lighttransmittance of greater than or equal to 70%. The third coloring layerpreferably has a 510-nm light transmittance of less than or equal to 60%and a 450-nm light transmittance of greater than or equal to 70%.

The emission spectrum of the light obtained from the firstlight-emitting element through the first coloring layer preferably has apeak value of greater than or equal to 620 nm and less than or equal to680 nm.

The first light-emitting element, the second light-emitting element, andthe third light-emitting element may include an electron-transport layerbetween a pair of electrodes and may each include a light-emitting layerbetween the pair of electrodes. In that case, the light-emitting layerin the first light-emitting element, that in the second light-emittingelement, and that in the third light-emitting element are preferablyseparated from each other. In addition, the first light-emittingelement, the second light-emitting element, and the third light-emittingelement preferably share the same electron-transport layer.

The first light-emitting element, the second light-emitting element, andthe third light-emitting element may include a hole-injection layerbetween the pair of electrodes. In that case, the first light-emittingelement, the second light-emitting element, and the third light-emittingelement preferably share the same hole-injection layer. Thehole-injection layer preferably contains a hole-transport material andan acceptor material.

The first light-emitting element, the second light-emitting element, andthe third light-emitting element may each include a hole-transport layerbetween the pair of electrodes. In that case, the hole-transport layerin the first light-emitting element, that in the second light-emittingelement, and that in the third light-emitting element are preferablyseparated from each other.

The first light-emitting element, the second light-emitting element, andthe third light-emitting element may each include a reflective electrodeand a transflective electrode as the pair of electrodes.

In the structure including the reflective electrode and thetransflective electrode, an optical path length between the reflectiveelectrode and the transflective electrode in the first light-emittingelement is preferably set so that emission intensity of red light can beincreased. An optical path length between the reflective electrode andthe transflective electrode in the second light-emitting element ispreferably set so that emission intensity of green light can beincreased. An optical path length between the reflective electrode andthe transflective electrode in the third light-emitting element ispreferably set so that emission intensity of blue light can beincreased.

The first light-emitting element, the second light-emitting element, andthe third light-emitting element may each include an EL layer betweenthe pair of electrodes. In that case, the EL layers included in thefirst light-emitting element, the second light-emitting element, and thethird light-emitting element are preferably EL layers that emit whitelight and that are formed using the same material. The EL layer includesat least a light-emitting layer. A plurality of EL layers may beincluded in each light-emitting element, and the EL layers may bestacked with a charge generation layer positioned therebetween. Toextract light with different colors efficiently from the EL layers thatemit white light in the light-emitting elements, optical path lengthsbetween the pair of electrodes are preferably adjusted depending on theemission color to form what is called a microcavity structure.

One or both of the first display region and the second display regionmay have a curved surface.

The first display panel may have a first curved surface and a secondcurved surface. The first curved surface includes the first displayregion, and the second curved surface does not include the first displayregion. In that case, the radius of curvature of the first curvedsurface may be larger than the radius of curvature of the second curvedsurface. For example, the radius of curvature of the first curvedsurface is larger than the radius of curvature of the second curvedsurface and is less than or equal to 10000 mm, and the radius ofcurvature of the second curved surface is greater than or equal to 1 mmand less than or equal to 100 mm. For example, the radius of curvatureof the first curved surface is greater than or equal to 10 mm and lessthan or equal to 10000 mm, and the radius of curvature of the secondcurved surface is greater than or equal to 1 mm and less than 10 mm.

The display device with any of the above structures may include alight-transmitting layer. In that case, the first display regionoverlaps with the region transmitting visible light with thelight-transmitting layer provided therebetween. The light-transmittinglayer includes a portion in which an average value of transmittance withrespect to light with a wavelength of greater than or equal to 450 nmand less than or equal to 700 nm is 80% or more.

The display device with any of the above structures may include a firstmodule and a second module. In that case, the first module includes thefirst display panel and at least one of a connector and an integratedcircuit. The second module includes the second display panel and atleast one of a connector and an integrated circuit.

One embodiment of the present invention is an electronic deviceincluding the display device with any of the above structures, and atleast one of an antenna, a battery, a housing, a camera, a speaker, amicrophone, and an operation button.

One embodiment of the present invention is a display panel that includesa first light-emitting element, a second light-emitting element, and athird light-emitting element. Light emitted from the firstlight-emitting element has a CIE 1931 chromaticity coordinate x ofgreater than 0.680 and less than or equal to 0.720 and a CIE 1931chromaticity coordinate y of greater than or equal to 0.260 and lessthan or equal to 0.320. Light emitted from the second light-emittingelement has a CIE 1931 chromaticity coordinate x of greater than orequal to 0.130 and less than or equal to 0.250 and a CIE 1931chromaticity coordinate y of greater than 0.710 and less than or equalto 0.810. Light emitted from the third light-emitting element has a CIE1931 chromaticity coordinate x of greater than or equal to 0.120 andless than or equal to 0.170 and a CIE 1931 chromaticity coordinate y ofgreater than or equal to 0.020 and less than 0.060. The firstlight-emitting element, the second light-emitting element, and the thirdlight-emitting element include a hole-injection layer and a firsthole-transport layer and each include a light-emitting layer. The firstlight-emitting element, the second light-emitting element, and the thirdlight-emitting element share the same hole-injection layer. The firstlight-emitting element, the second light-emitting element, and the thirdlight-emitting element share the same first hole-transport layer. Thelight-emitting layer in the first light-emitting element, that in thesecond light-emitting element, and that in the third light-emittingelement are separated from each other. In the third light-emittingelement, the first hole-transport layer is in contact with thehole-injection layer and the light-emitting layer. It is preferable thatthe first light-emitting element and the second light-emitting elementeach include a second hole-transport layer. It is preferable that ineach of the first light-emitting element and the second light-emittingelement, the first hole-transport layer be in contact with thehole-injection layer and the second hole-transport layer be in contactwith the light-emitting layer. The hole-injection layer and the firsthole-transport layer preferably contain the same material. Thelight-emitting layer and the second hole-transport layer preferablycontain the same material. The second hole-transport layer preferablycontains a material with a HOMO level shallower than a HOMO level of amaterial contained in the first hole-transport layer. A display device,a module, and an electronic device each including the above displaypanel are also embodiments of the present invention.

One embodiment of the present invention can increase the size of adisplay device. One embodiment of the present invention can provide adisplay device including a wide display region in which a seam is lesslikely to be noticed. One embodiment of the present invention canprovide a display device that can display an image with a wide colorgamut. One embodiment of the present invention can suppress displayunevenness or luminance unevenness of a display device. One embodimentof the present invention can reduce the thickness or weight of a displaydevice. One embodiment of the present invention can provide a displaydevice that can display an image along a curved surface. One embodimentof the present invention can provide a highly browsable display device.One embodiment of the present invention can provide a novel displaydevice.

Note that the description of these effects does not preclude theexistence of other effects. One embodiment of the present invention doesnot necessarily achieve all the effects listed above. Other effects canbe derived from the description of the specification, the drawings, andthe claims.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A to 1C are a top view and cross-sectional views illustrating anexample of a display panel.

FIGS. 2A and 2B are a top view and a cross-sectional view illustratingan example of a display device.

FIGS. 3A and 3B are a top view and a cross-sectional view illustratingan example of a display device.

FIGS. 4A to 4G are cross-sectional views illustrating examples of adisplay device and examples of an optical member.

FIGS. 5A to 5E are top views illustrating examples of a display paneland perspective views illustrating an example of a display device.

FIGS. 6A to 6E are cross-sectional views illustrating examples of adisplay device.

FIGS. 7A to 7D are cross-sectional views illustrating examples of adisplay device.

FIGS. 8A to 8C are top views and a cross-sectional view illustrating anexample of a display panel.

FIGS. 9A to 9C are a top view and cross-sectional views illustrating anexample of a display panel.

FIGS. 10A and 10B illustrate examples of a display device.

FIG. 11 is a chromaticity diagram showing chromaticity ranges of displaydevices.

FIGS. 12A to 12D illustrate examples of a light-emitting element.

FIGS. 13A and 13B illustrate an example of a display device.

FIGS. 14A to 14C are top views and a cross-sectional view illustratingexamples of a display panel.

FIG. 15 is a cross-sectional view illustrating an example of a displaydevice.

FIG. 16 is a cross-sectional view illustrating an example of a displaypanel.

FIG. 17 is a cross-sectional view illustrating an example of a displaypanel.

FIG. 18 is a cross-sectional view illustrating an example of a displaypanel.

FIGS. 19A and 19B are perspective views illustrating an example of atouch panel.

FIG. 20 is a cross-sectional view illustrating an example of a touchpanel.

FIGS. 21A and 21B are perspective views illustrating an example of atouch panel.

FIGS. 22A to 22F illustrate examples of electronic devices and alighting device.

FIGS. 23A1, 23A2, 23B, 23C, 23D, 23E, 23F, 23G, 23H, and 23I illustrateexamples of electronic devices.

FIGS. 24A and 24B illustrate an example of a display device.

FIG. 25 illustrates a light-emitting element in Example 1.

FIG. 26 is a chromaticity diagram of a light-emitting element in Example1 obtained by calculation.

FIG. 27A is a top view illustrating a display panel in Example 2 andFIGS. 27B and 27C are a top view and a cross-sectional view illustratinga display device in Example 2.

FIG. 28 shows a photograph of an image displayed by a display device inExample 2.

FIG. 29A is a side view illustrating a display device in Example 2 andFIG. 29B is a perspective view illustrating a circularly polarizingplate.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments are described in detail with reference to the drawings. Notethat the present invention is not limited to the following description.It is readily appreciated by those skilled in the art that modes anddetails of the present invention can be modified in various ways withoutdeparting from the spirit and scope of the present invention. Thus, thepresent invention should not be construed as being limited to thedescription in the following embodiments.

Note that in the structures of the invention described below, the sameportions or portions having similar functions are denoted by the samereference numerals in different drawings, and description of suchportions is not repeated. Furthermore, the same hatching pattern isapplied to portions having similar functions, and the portions are notespecially denoted by reference numerals in some cases.

The position, size, range, or the like of each component illustrated indrawings is not accurately represented in some cases for easyunderstanding. Therefore, the disclosed invention is not necessarilylimited to the position, size, range, or the like disclosed in thedrawings.

Note that the terms “film” and “layer” can be interchanged with eachother depending on the case or circumstances. For example, the term“conductive layer” can be changed into the term “conductive film”. Inaddition, the term “insulating film” can be changed into the term“insulating layer”.

Embodiment 1

In this embodiment, a display device of one embodiment of the presentinvention is described with reference to FIGS. 1A to 1C, FIGS. 2A and2B, FIGS. 3A and 3B, FIGS. 4A to 4G, FIGS. 5A to 5E, FIGS. 6A to 6E,FIGS. 7A to 7D, FIGS. 8A to 8C, FIGS. 9A to 9C, FIGS. 10A and 10B, andFIG. 11.

When a plurality of display panels are arranged in one or moredirections (e.g., in one column or in matrix), a display device with alarge display region can be manufactured.

In the case where a large display device is manufactured using aplurality of display panels, each of the display panels is not requiredto be large. Thus, an apparatus for manufacturing the display panel doesnot need to be increased in size, whereby space-saving can be achieved.Furthermore, since an apparatus for manufacturing small- andmedium-sized display panels can be used and a novel apparatus formanufacturing large display devices is unnecessary, manufacturing costcan be reduced. In addition, a decrease in yield caused by an increasein the size of a display panel can be suppressed.

A display device including a plurality of display panels has a largerdisplay region than a display device including one display panel whenthe display panels have the same size, and has an effect of displayingmore information at a time, for example.

However, each of the display panels has a non-display region thatsurrounds a display region. Thus, for example, in the case where outputimages of a plurality of display panels are used to display one image,the image appears divided to a user of the display device.

Making the non-display regions of the display panels small (usingdisplay panels with narrow frames) can prevent an image displayed on thedisplay panels from appearing divided; however, it is difficult tototally remove the non-display regions of the display panel.

A small non-display region of the display panel leads to a decrease inthe distance between an end portion of the display panel and an elementin the display panel, in which case the element easily deteriorates byimpurities entering from outside the display panel in some cases.

Thus, in one embodiment of the present invention, a plurality of displaypanels are arranged to partly overlap with one another. In two displaypanels overlapping with each other, at least a display panel positionedon the display surface side (upper side) includes a region transmittingvisible light and a display region adjacent to each other. In oneembodiment of the present invention, a display region of a display panelpositioned on a lower side and the region transmitting visible light ofthe display panel on the upper side overlap with each other. Thus, anon-display region between the display regions of the two overlappingdisplay panels can be reduced and even removed. As a result, alarge-sized display device in which a seam between the display panels ishardly seen by the user can be obtained.

At least part of a non-display region of the display panel on the upperside transmits visible light, and can overlap with the display region ofthe display panel on the lower side. Furthermore, at least part of anon-display region of the display panel on the lower side can overlapwith the display region of the display panel on the upper side or aregion that blocks visible light thereof. It is not necessary to reducethe areas of the non-display regions because a reduction in the area ofthe frame of the display device (a reduction in area except a displayregion) is not affected by these regions.

A large non-display region of the display panel leads to an increase inthe distance between the end portion of the display panel and an elementin the display panel, in which case the deterioration of the element dueto impurities entering from outside the display panel can be suppressed.For example, in the case where an organic EL element is used as adisplay element, impurities such as moisture or oxygen are less likelyto enter (or less likely to reach) the organic EL element from outsidethe display panel as the distance between the end portion of the displaypanel and the organic EL element increases. Since a sufficient area ofthe non-display region of the display panel can be secured in thedisplay device of one embodiment of the present invention, a highlyreliable large display device can be fabricated even when a displaypanel including an organic EL element or the like is used.

In one embodiment of the present invention, a display panel that candisplay an image with a wide color gamut is used. In that case, adisplay device that can display an image with a wide color gamut can bemanufactured. Specifically, the display panel includes a plurality oflight-emitting elements. Light emitted from a first light-emittingelement has a CIE 1931 chromaticity coordinate x of greater than 0.680and less than or equal to 0.720 and a CIE 1931 chromaticity coordinate yof greater than or equal to 0.260 and less than or equal to 0.320. Lightemitted from a second light-emitting element has a CIE 1931 chromaticitycoordinate x of greater than or equal to 0.130 and less than or equal to0.250 and a CIE 1931 chromaticity coordinate y of greater than 0.710 andless than or equal to 0.810. Light emitted from a third light-emittingelement has a CIE 1931 chromaticity coordinate x of greater than orequal to 0.120 and less than or equal to 0.170 and a CIE 1931chromaticity coordinate y of greater than or equal to 0.020 and lessthan 0.060. As each light-emitting element, an organic EL elementincluding an EL layer between a pair of electrodes is suitable. As thepair of electrodes, a reflective electrode and a transflective electrodeare suitable.

The light-emitting elements for different colors preferably includeseparate light-emitting layers. Since a display device of one embodimentof the present invention is composed of a plurality of display panels,each display panel can have a relatively small size. Thus, the alignmentaccuracy of a metal mask is high, leading to higher yield in separatecoloring. In addition, since an application example of the displaydevice of one embodiment of the present invention is a large-sizedelectronic device, the resolution of the display panel can be relativelylow. Accordingly, the display device of one embodiment of the presentinvention has an advantage when employing light-emitting elements thatare formed by a separate coloring method. Note that when the resolutionof the display panel is high, the light-emitting layer of onelight-emitting element partly overlaps with that of anotherlight-emitting element in some cases. In this specification and thelike, separation of light-emitting layers for different colors does notnecessarily mean spatial separation between the light-emitting layersand sometimes means electrical insulation from each other.

The light-emitting elements may have any of a bottom-emission structureand a top-emission structure. It is particularly preferable to usetop-emission light-emitting elements.

The light-emitting elements each preferably have a microcavitystructure. Specifically, the optical distance between the pair ofelectrodes is preferably adjusted in the following manner: in the ELlayers, not only the light-emitting layer but also a layer of anotherkind (e.g., a hole-transport layer) is formed separately for each of thelight-emitting elements for different colors; and other layers areshared by the light-emitting elements for different colors. Thisstructure simplifies the process and makes it possible to provide adisplay panel from which light can be efficiently extracted and whichcan display an image with a wide color gamut.

Structural Example 1 of Display Panel

FIG. 1A is a top view of a display panel 100.

The display panel 100 includes a display region 101 and a region 102.Here, the region 102 is a portion other than the display region 101 ofthe display panel 100 in a top view. The region 102 can also be referredto as a non-display region.

The region 102 includes a region 110 transmitting visible light and aregion 120 blocking visible light. The region 110 transmitting visiblelight and the region 120 blocking visible light are each adjacent to thedisplay region 101.

The region 110 transmitting visible light and the region 120 blockingvisible light can each be provided along part of the outer end portionof the display region 101. In the display panel 100 illustrated in FIG.1A, the region 110 transmitting visible light is provided along one sideof the display region 101. The region 110 transmitting visible light maybe provided along two or more sides of the display region 101. Theregion 110 transmitting visible light is preferably in contact with thedisplay region 101 and provided so as to extend to an end portion of thedisplay panel as illustrated in FIG. 1A.

In the display panel 100 in FIG. 1A, the region 120 blocking visiblelight is provided along two sides of the display region 101. The region120 blocking visible light may extend close to an end portion of thedisplay panel.

Note that in the region 102 illustrated in FIG. 1A, a region other thanthe region 110 transmitting visible light and the region 120 blockingvisible light does not necessarily have visible light transmittance.

The display region 101 includes a plurality of pixels arranged in amatrix and can display an image. One or more display elements areprovided in each pixel. As the display element, a light-emitting elementsuch as an EL element, an electrophoretic element, a display elementwith use of micro electro mechanical systems (MEMS), a liquid crystalelement, or the like can be used, for example.

In one embodiment of the present invention, the display panel 100 candisplay an image with a wide color gamut by including organic ELelements, as described above.

A material that transmits visible light is used for the region 110transmitting visible light. A substrate, a bonding layer, or the likeincluded in the display panel 100 may also be used, for example. Theregion 110 transmitting visible light preferably has a higher visiblelight transmittance to increase the extraction efficiency of light fromthe display panel under the region 110 transmitting visible light. Theregion 110 transmitting visible light preferably has a transmittance ofhigher than or equal to 70%, further preferably higher than or equal to80%, and still further preferably higher than or equal to 90% on averagewith respect to light with a wavelength greater than or equal to 400 nmand less than or equal to 700 nm.

In the region 120 blocking visible light, for example, a wiringelectrically connected to the pixels (specifically, transistors, displayelements, or the like) included in the display region 101 is provided.In addition to such a wiring, driver circuits (e.g., a scan line drivercircuit or a signal line driver circuit) for driving the pixels can beprovided.

The display panel can include at least one of the scan line drivercircuit and the signal line driver circuit. Alternatively, the displaypanel may include neither the scan line driver circuit nor the signalline driver circuit. For example, an IC serving as at least one of thescan line driver circuit and the signal line driver circuit can beelectrically connected to the display panel. The IC can be mounted on adisplay panel by a COG method or a COF method. Alternatively, an FPC, atape automated bonding (TAB) tape, a TCP, or the like on which the IC ismounted can be connected to a display panel.

Furthermore, the region 120 blocking visible light includes a terminalelectrically connected to an FPC or the like (also referred to as aconnection terminal), a wiring electrically connected to the terminal,and the like. Note that in the case where the terminal, wiring, and thelike transmit visible light, the terminal, wiring, and the like can beprovided to extend to the region 110 transmitting visible light.

Here, a width W of the region 110 transmitting visible light in FIG. 1Ais preferably greater than or equal to 0.5 mm and less than or equal to150 mm, further preferably greater than or equal to 1 mm and less thanor equal to 100 mm, and still further preferably greater than or equalto 2 mm and less than or equal to 50 mm. In the case where the width Wof the region 110 transmitting visible light is different between thedisplay panels, or in the case where the width varies depending on theposition in one display panel, the shortest length is preferably withinthe above range. The region 110 transmitting visible light serves as asealing region. As the width W of the region 110 transmitting visiblelight is larger, the distance between the end portion of the displaypanel 100 and the display region 101 can become longer, in which caseentry of an impurity such as water from the outside into the displayregion 101 can be suppressed. Note that the width W of the region 110transmitting visible light corresponds to the shortest distance betweenthe display region 101 and the end portion of the display panel 100 insome cases.

In the case where an organic EL element is used as the display element,for example, the width W of the region 110 transmitting visible light isset to be greater than or equal to 1 mm, whereby deterioration of theorganic EL element can be effectively suppressed, which leads to animprovement in reliability. Note that also in a portion other than theregion 110 transmitting visible light, the distance between the endportion of the display region 101 and the end portion of the displaypanel 100 is preferably in the above range.

FIGS. 1B and 1C are cross-sectional views along dashed-dotted line X1-Y1in FIG. 1A.

The display panel 100 illustrated in FIG. 1B includes a substrate 201, abonding layer 203, an insulating layer 205, an insulating layer 208, anelement layer 209, a substrate 211, a bonding layer 221, and aconnection terminal 223.

The bonding layer 203 is positioned between the substrate 201 and theinsulating layer 205. The bonding layer 221 is positioned between thesubstrate 211 and the insulating layer 205.

The display region 101 includes the element layer 209. The element layer209 includes a display element. The display element is positionedbetween the insulating layer 205 and the insulating layer 208.

In the region 120 blocking visible light, the connection terminal 223 ispositioned over the insulating layer 205. The connection terminal 223includes an exposed portion not overlapping with the bonding layer 221or the substrate 211.

A method for manufacturing the display panel illustrated in FIG. 1B isdescribed. First, layers to be peeled (such as the insulating layer 205,the element layer 209, the insulating layer 208, and the connectionterminal 223) are formed over a formation substrate with a peeling layerprovided therebetween. The substrate 211 is attached to the layers to bepeeled with the use of the bonding layer 221. Then, the formationsubstrate is peeled with the use of the peeling layer, and the substrate201 is attached to the layers to be peeled with the use of the bondinglayer 203. In this manner, the layers to be peeled that are formed overthe formation substrate can be transferred to the substrate 201.

The display panel 100 illustrated in FIG. 1C includes the substrate 201,the bonding layer 203, the insulating layer 205, the element layer 209,the substrate 211, a bonding layer 213, an insulating layer 215, afunctional layer 219, the bonding layer 221, and the connection terminal223.

The bonding layer 203 is positioned between the substrate 201 and theinsulating layer 205. The bonding layer 213 is positioned between thesubstrate 211 and the insulating layer 215. The bonding layer 221 ispositioned between the insulating layer 205 and the insulating layer215.

The display region 101 includes the element layer 209. The displayregion 101 may further include the functional layer 219.

The element layer 209 includes a display element. The display element ispositioned between the insulating layer 205 and the bonding layer 221.

The functional layer 219 includes at least one of a coloring layer(e.g., a color filter), a light-blocking layer (e.g., a black matrix),and a sensor (e.g., a touch sensor). The functional layer 219 ispositioned between the insulating layer 215 and the bonding layer 221.

In the region 120 blocking visible light, the connection terminal 223 ispositioned over the insulating layer 205. The connection terminal 223includes an exposed portion that does not overlap with the bonding layer221, the insulating layer 215, the bonding layer 213, or the substrate211.

A method for manufacturing the display panel illustrated in FIG. 1C isdescribed. First, first layers to be peeled (such as the insulatinglayer 205, the element layer 209, and the connection terminal 223) areformed over a first formation substrate with a first peeling layerprovided therebetween. Furthermore, second layers to be peeled (theinsulating layer 215 and the functional layer 219) are formed over asecond formation substrate with a second peeling layer providedtherebetween. The first formation substrate and the second formationsubstrate are attached to each other with the use of the bonding layer221. Then, the first formation substrate and the second formationsubstrate are peeled with the use of the first peeling layer and thesecond peeling layer, respectively. To the surface that is exposed bypeeling the first formation substrate, the substrate 201 is attachedwith the use of the bonding layer 203. To the surface that is exposed bypeeling the second formation substrate, the substrate 211 is attachedwith the use of the bonding layer 213. In this manner, the layers to bepeeled that are formed over the formation substrates can be transferredto the substrates 201 and 211.

In the method for manufacturing a display panel of one embodiment of thepresent invention, each of the functional elements and the like includedin the display panel is formed over the formation substrate; thus, evenin the case where a high-resolution display panel is manufactured, highalignment accuracy of the substrate included in the display panel is notrequired. Thus, even when a flexible substrate is used for the displaypanel, the substrate can be attached easily. In addition, since thefunctional element and the like can be fabricated with hightemperatures, a highly reliable display panel can be obtained.

The region 110 transmitting visible light reflects or absorbs part ofvisible light (e.g., light with a wavelength greater than or equal to400 nm and less than or equal to 700 nm). When the region 110transmitting visible light reflects external light, a user of thedisplay device can easily notice an area in which two or more displaypanels overlap with each other (hereinafter, also referred to as anoverlapping area). The user of the display device can easily notice theoverlapping area particularly when the display panel on the lower sidedoes not perform display or performs black display. Moreover, theluminance (brightness) of display on the display panel on the lower sideis different between a portion seen through the region 110 transmittingvisible light and a portion seen not through the region.

The smaller the differences between layers included in the region 110transmitting visible light are, the more the reflection of light in theregion 110 transmitting visible light can be suppressed. Accordingly,the overlapping area is not easily noticed by a user of the displaydevice. Therefore, a display device including a wide display region inwhich a seam is less likely to be noticed can be fabricated.

In the region 110 transmitting visible light, the difference inrefractive index between two layers that are in contact with each otheris preferably smaller than or equal to 0.20, further preferably smallerthan or equal to 0.15, still further preferably smaller than or equal to0.10. For example, in FIG. 1B, each of the differences in refractiveindex between the substrate 201 and the bonding layer 203, between thebonding layer 203 and the insulating layer 205, between the insulatinglayer 205 and the bonding layer 221, and between the bonding layer 221and the substrate 211 is preferably smaller than or equal to 0.20. Forexample, in FIG. 1C, each of the differences in refractive index betweenthe substrate 201 and the bonding layer 203, between the bonding layer203 and the insulating layer 205, between the insulating layer 205 andthe bonding layer 221, between the bonding layer 221 and the insulatinglayer 215, between the insulating layer 215 and the bonding layer 213,and between the bonding layer 213 and the substrate 211 is preferablysmaller than or equal to 0.20. It is preferable to reduce the differencein refractive index between layers included in the region 110transmitting visible light because the reflection of light due to thedifference in refractive index can be suppressed. The difference inrefractive index between layers included in the region 110 transmittingvisible light is preferably smaller than or equal to 0.20, furtherpreferably smaller than or equal to 0.15, still further preferablysmaller than or equal to 0.10.

By reducing the number of interfaces which are included in the region110 transmitting visible light and at which a difference in refractiveindex is large, the visible light transmittance in the region 110transmitting visible light can be increased. Thus, the difference in theluminance (brightness) of display on the display panel on the lower sidebetween a portion seen through the region 110 transmitting visible lightand a portion seen not through the region can be small. Accordingly, thedisplay unevenness or luminance unevenness of the display device can besuppressed.

The substrates 201 and 211 are preferably flexible. Using the flexiblesubstrates can increase the flexibility of the display panel. Inmanufacturing the display panel of this embodiment, an insulating layer,a transistor, a display element, and the like are formed over aformation substrate and then transferred to the substrate 201 and thesubstrate 211. Therefore, the range of choices for the materials for thesubstrate 201 and the substrate 211 is wider than that in the case offorming an insulating layer, a transistor, a display element, and thelike directly on the substrate 201 or the substrate 211.

The thickness of each of the substrates 201 and 211 is preferablygreater than or equal to 1 μm and less than or equal to 100 μm, furtherpreferably greater than or equal to 1 μm and less than or equal to 50μm, still further preferably greater than or equal to 1 μm and less thanor equal to 25 μm. By reducing the thicknesses of the substrates, a stepcan be reduced when display panels overlap with each other.

Each of the substrates 201 and 211 preferably has a transmittance ofhigher than or equal to 70%, further preferably higher than or equal to80%, and still further preferably higher than or equal to 90% on averagewith respect to light with a wavelength longer than or equal to 450 nmand shorter than or equal to 700 nm. The higher the visible lighttransmittance of the substrates, the more the visible lighttransmittance in the region 110 transmitting visible light can beincreased and the more extraction efficiency of light of the displaydevice can be increased.

Each of the substrates 201 and 211 has a glass transition temperaturepreferably higher than or equal to 150° C., further preferably higherthan or equal to 200° C., and still further preferably higher than orequal to 250° C. The higher the heat resistance of the substrates is,the more defects of the display panel due to preservation in hightemperature environment, a pressure-bonding step of an FPC, or the likecan be reduced.

The coefficient of thermal expansion of each of the substrates 201 and211 is preferably lower than or equal to 60 ppm/° C., further preferablylower than or equal to 30 ppm/° C., still further preferably lower thanor equal to 15 ppm/° C. The lower the coefficient of thermal expansionof the substrate is, the less the display panel is affected by atemperature change of an environment in which the display panel isstored. For example, even when the temperature of a storage environmentis changed, generation of creases in the display panel and a crack in aninorganic film can be suppressed.

The coefficient of humidity expansion of each of the substrates 201 and211 is preferably lower than or equal to 100 ppm/% RH, furtherpreferably lower than or equal to 50 ppm/% RH, still further preferablylower than or equal to 20 ppm/% RH. The lower the coefficient ofhumidity expansion of the substrate is, the less the display panel isaffected by a humidity change of an environment in which the displaypanel is stored. For example, even when the humidity of a storageenvironment is changed, generation of creases in the display panel and acrack in an inorganic film can be suppressed.

Structure Example 1 of Display Device

FIG. 2A is a top view of a display device 12. The display device 12illustrated in FIG. 2A includes three display panels 100 illustrated inFIG. 1A arranged in one direction (a lateral direction). FIG. 2Aillustrates an example where each of the display panels is electricallyconnected to an FPC.

In this embodiment, to distinguish the display panels from each other,the same components included in the display panels from each other, orthe same components relating to the display panels from each other,letters are added to reference numerals in some cases. Unless otherwisespecified, “a” is added to reference numerals for a display panel andcomponents placed on the lowest side (the side opposite to the displaysurface side), and to one or more display panels and components placedthereover, “b”, “c”, and the like are added in alphabetical order fromthe lower side. Furthermore, unless otherwise specified, in describing astructure in which a plurality of display panels are included, lettersare not added when a common part of the display panels or the componentsis described.

The display device 12 in FIG. 2A includes a display panel 100 a, adisplay panel 100 b, and a display panel 100 c.

The display panel 100 b is placed so that part of the display panel 100b is stacked over an upper side (a display surface side) of the displaypanel 100 a. Specifically, a region 110 b transmitting visible light ofthe display panel 100 b is provided to overlap with a display region 101a of the display panel 100 a. A region 120 b blocking visible light ofthe display panel 100 b is provided so as not to overlap with thedisplay region 101 a of the display panel 100 a. A display region 101 bof the display panel 100 b is provided to overlap with a region 102 a ofthe display panel 100 a and a region 120 a blocking visible light of thedisplay panel 100 a.

Similarly, the display panel 100 c is placed so as to partly overlapwith an upper side (display surface side) of the display panel 100 b.Specifically, a region 110 c transmitting visible light of the displaypanel 100 c is provided to overlap with the display region 101 b of thedisplay panel 100 b. A region 120 c blocking visible light of thedisplay panel 100 c is provided so as not to overlap with the displayregion 101 b of the display panel 100 b. A display region 101 c of thedisplay panel 100 c is provided to overlap with a region 102 b of thedisplay panel 100 b and the region 120 b blocking visible light of thedisplay panel 100 b.

The region 110 b transmitting visible light is provided to overlap withthe display region 101 a; thus, a user of the display device 12 can seethe entire image on the display region 101 a even when the display panel100 b overlaps with a display surface of the display panel 100 a.Similarly, the region 110 c transmitting visible light is provided tooverlap with the display region 101 b; thus, a user of the displaydevice 12 can see the entire image on the display region 101 b even whenthe display panel 100 c overlaps with a display surface of the displaypanel 100 b.

The display region 101 b of the display panel 100 b overlaps with uppersides of the region 102 a and the region 120 a blocking visible light;as a result, a non-display region does not exist between the displayregion 101 a and the display region 101 b. Similarly, the display region101 c of the display panel 100 c overlaps with upper sides of the region102 b and the region 120 b blocking visible light; as a result, anon-display region does not exist between the display region 101 b andthe display region 101 c. Thus, a region where the display region 101 a,the display region 101 b, and the display region 101 c are placedseamlessly can serve as a display region 13 of the display device 12.

FIG. 2B is a cross-sectional view along dashed-dotted line X2-Y2 in FIG.2A.

The display panels 100 a and 100 b illustrated in FIG. 2B each have thesame structure as the structure of the display panel illustrated in FIG.1C.

To reduce the step between two adjacent display panels 100, thethickness of the display panel 100 is preferably small. For example, thethickness of the display panel 100 is preferably less than or equal to 1mm, further preferably less than or equal to 300 μm, still furtherpreferably less than or equal to 100 μm. The display panel is preferablythin because the thickness or weight of the whole display device canalso be reduced.

When air exists between the region transmitting visible light of theupper display panel and the display region of the lower display panel,part of light extracted from the display region is reflected at theinterface between the display region and air and the interface betweenair and the region transmitting visible light, which may result in adecrease in luminance of the display. As a result, the light extractionefficiency of a region in which a plurality of display panels overlapwith each other might be decreased. In addition, a difference inluminance of the display region of the lower display panel might occurbetween a portion overlapping with the region transmitting visible lightof the upper display panel and a portion not overlapping with the regiontransmitting visible light of the upper display panel, so that a seambetween the display panels is easily noticed by a user in some cases.

As illustrated in FIG. 2B, the display device 12 includes alight-transmitting layer 103 between the display region 101 a and theregion 110 b transmitting visible light. The light-transmitting layer103 has a refractive index higher than that of air and transmits visiblelight. Thus, air can be prevented from entering between the displayregion 101 a and the region 110 b transmitting visible light, so thatthe interface reflection due to a difference in refractive index can besuppressed. In addition, display unevenness or luminance unevenness ofthe display device can be reduced.

Note that the light-transmitting layer 103 preferably has a high visiblelight transmittance because the light extraction efficiency of thedisplay device can be increased. The light-transmitting layer 103preferably has a transmittance of higher than or equal to 80% andfurther preferably higher than or equal to 90% on average with respectto light with a wavelength greater than or equal to 400 nm and less thanor equal to 700 nm.

The difference in refractive index between the light-transmitting layerand a layer in contact with the light-transmitting layer is preferablyas small as possible because the light reflection can be suppressed. Forexample, the refractive index of the light-transmitting layer is higherthan that of air, and preferably higher than or equal to 1.3 and lowerthan or equal to 1.8. The difference in refractive index between thelight-transmitting layer and the layer in contact with thelight-transmitting layer (e.g., a substrate included in the displaypanel) is preferably lower than or equal to 0.30, further preferablylower than or equal to 0.20, and still further preferably lower than orequal to 0.15.

It is preferable that the light-transmitting layer be detachably incontact with at least one of the lower display panel and the upperdisplay panel. In the case where the display panels included in thedisplay device are individually detachable, when malfunction occurs inone of the display panels, for example, only the defective display panelcan be easily replaced with a new display panel. The continuous use ofthe other display panel enables the display device to be used longer andat lower cost.

When there is no need to attach and detach the display panels, thedisplay panels are fixed to each other with the light-transmitting layerincluding a material having an adhesive property (an adhesive or thelike).

Either of an inorganic material and an organic material can be used forthe light-transmitting layer. A liquid substance, a gelatinoussubstance, or a solid substance can be used for the light-transmittinglayer.

For the light-transmitting layer, a liquid substance such as water, anaqueous solution, a fluorine-based inactive liquid, a refractive liquid,or silicone oil can be used, for example.

In the case where the display device is inclined to the horizontal plane(a plane perpendicular to a direction in which gravity acts) or in thecase where the display device is placed so as to be perpendicular to thehorizontal plane, the viscosity of a liquid substance is preferably 1mPa·s or more, further preferably 1 Pa·s or more, still furtherpreferably 10 Pa·s or more, and yet still further preferably 100 Pa·s ormore. In the case where the display device is placed so as to beparallel to the horizontal plane, for example, the viscosity of theliquid substance is not limited thereto.

The light-transmitting layer is preferably inactive because damage toanother layer included in the display device can be suppressed, forexample.

A material contained in the light-transmitting layer is preferablynonvolatile. Accordingly, entry of air into the interface due tovolatilization of a material used for the light-transmitting layer canbe suppressed.

For the light-transmitting layer, a high molecular material can be used.For example, a resin such as an epoxy resin, an acrylic resin, asilicone resin, a phenol resin, a polyimide resin, an imide resin, apolyvinyl chloride (PVC) resin, a polyvinyl butyral (PVB) resin, or anethylene vinyl acetate (EVA) resin can be used. Alternatively, atwo-component-mixture-type resin may be used. For example, an adhesivesheet or any of a variety of curable adhesives such as a reactivecurable adhesive, a thermosetting adhesive, an anaerobic adhesive, and aphotocurable adhesive such as an ultraviolet curable adhesive containingat least one of the above resins may be used. The adhesives do not needto be cured in the case where, for example, the display panels are notfixed to each other.

The light-transmitting layer preferably has high self-attachability toan object. In addition, the light-transmitting layer preferably has highseparability against an object. After the light-transmitting layerattached to the display panel is separated from the display panel, it ispreferable that the light-transmitting layer be able to be attached tothe display panel again.

It is preferable that the light-transmitting layer have no adhesivenessor low adhesiveness. In that case, attachment and separation of thelight-transmitting layer to and from an object can be repeated withoutdamaging or contaminating a surface of the object.

As the light-transmitting layer, a film having attachability or a filmhaving adhesiveness can be used, for example. In the case where anattachment film having a stacked-layer structure of an attachment layeror an adhesive layer and a base material is used, the attachment layeror the adhesive layer may function as the light-transmitting layer ofthe display device, and the base material may function as a substrateincluded in the display panel. Note that the display device may have asubstrate in addition to the base material in the attachment film. Theattachment film may include an anchor layer between the attachment layeror the adhesive layer and the base material. The anchor layer has afunction of enhancing the adhesiveness between the attachment layer orthe adhesive layer and the base material. In addition, the anchor layerhas a function of smoothing a surface of the base material coated withthe attachment layer or the adhesive layer. In this manner, bubbles arenot easily generated between the object and the light-transmittinglayer. A film in which a polyester film and a silicone resin layerhaving attachability are stacked can be preferably used in the displaydevice, for example.

The thickness of the light-transmitting layer is not particularlylimited and may be greater than or equal to 1 μm and less than or equalto 50 μm, for example. The thickness of the light-transmitting layer canbe greater than 50 μm; however, in the case of manufacturing a flexibledisplay device, the thickness of the light-transmitting layer ispreferably set such that the flexibility of the display device is notreduced. For example, the thickness of the light-transmitting layer ispreferably greater than or equal to 10 μm and less than or equal to 30μm. The thickness of the light-transmitting layer can be less than 1 μm.

The display region 101 a overlaps with the region 110 b transmittingvisible light with the light-transmitting layer 103 providedtherebetween. Thus, entry of air between the display region 101 a andthe region 110 b transmitting visible light can be suppressed, so thatinterface reflection due to a difference in refractive index can bereduced.

Accordingly, a difference in luminance of the display region 101 abetween a portion overlapping with the region 110 b transmitting visiblelight and a portion not overlapping with the region 110 b transmittingvisible light can be suppressed, so that a seam between the displaypanels can be less likely to be noticed by a user of the display device.In addition, display unevenness or luminance unevenness of the displaydevice can be suppressed.

The region 120 a blocking visible light and an FPC 112 a each overlapwith the display region 101 b. Thus, a sufficient area of a non-displayregion can be secured and a seamless display region can be increased insize, so that a highly reliable large display device can be fabricated.

Structure Example 2 of Display Device

FIG. 3A is a top view of the display device 12. FIG. 3B is across-sectional view taken along dashed-dotted line X3-Y3 in FIG. 3A.

The display device 12 illustrated in FIGS. 3A and 3B has a structure inwhich an optical member 240 is placed on the outermost surface of thedisplay device 12 illustrated in FIGS. 2A and 2B. Other components aresimilar to those in FIGS. 2A and 2B; thus, the detailed descriptionthereof is omitted.

The optical member 240 is provided at least in the display region 13.FIG. 3A illustrates an example in which the optical member 240 overlapswith the entire areas of display panels. The optical member 240 and eachof the display panels are preferably adhered closely. At least parts ofthe optical member 240 and each of the display panels may be fixed withan adhesive or the like, and the optical member 240 and each of thedisplay panels are not necessarily fixed. For example, the opticalmember 240 and each of the display panels may be independently fixed toa housing included in the display device 12 or an electronic device.

As the optical member 240, one or more of a polarizing member, aretardation member, an anti-reflection member, and the like can be used.Moreover, hard coat treatment may be performed on the outermost surfaceof the optical member 240.

Examples of the polarizing member include a polarizing plate and apolarizing film.

Examples of the retardation member include a retardation plate and aretardation film.

Examples of the anti-reflection member include an anti-reflection (AR)film, a low-reflection (LR) film, and an anti-glare (AG) film (alsoreferred to as a non-glare film). Furthermore, an anti-reflection plateand an anti-reflection film that each have the same function as that ofany of these films are also examples of the anti-reflection member.

Examples of the structure of the optical member 240 are described withreference to FIGS. 4A to 4G.

The optical member 240 illustrated in FIG. 4A includes ananti-reflection member 291.

Each of an AR film, an LR film, an AG film, and the like can be directlyattached to the display panels.

When an AR film or an LR film is used for the anti-reflection member291, the reflection of external light from a surface of the displaydevice 12 can be suppressed.

When an AG film is used for the anti-reflection member 291, reflectionof surroundings of the display device 12 on the surface of the displaydevice can be suppressed by scattering external light.

The optical member 240 illustrated in FIG. 4B includes theanti-reflection member 291 and a support member 292. The support member292 is arranged closer to the display panel than the anti-reflectionmember 291 is.

The optical member 240 preferably has a structure in which one or moreof a polarizing member, a retardation member, an anti-reflection member,and the like is/are attached to the support member 292 that transmitsvisible light.

Overlapping a plurality of display panels with each other causes a stepbetween the display panels. Thus, in the case where one optical member240 is attached to a plurality of display panels, air is likely to enterthe interface between the optical member 240 and the display panels.Moreover, by attaching one optical member 240 to a plurality of displaypanels, the display panels cannot be detached in some cases. In the casewhere the optical members 240 are attached to the display panels one byone, effort is required, and thus manufacturing time might be increased.

The use of the support member 292 can increase the strength of theoptical member 240, increase the thickness of the optical member 240, orfacilitate the handling of the optical member 240, for example. Thus,the optical member 240 can be sufficiently closely attached to thedisplay panels, and the amount of air at the interface between theoptical member 240 and the display panels can be minimized. Stepsbetween the plurality of display panels and creases of the displaypanels can be reduced by attaching the optical member 240 to the displaypanels sufficiently closely. The optical member 240 and the displaypanels are preferably fixed to be sufficiently closely attached to eachother. The number of points for fixing the optical member 240 and thedisplay panels is as small as possible; accordingly, the fabricationprocess of the display device can be simplified and the yield of thedisplay device can be improved.

As the support member 292, for example, a plastic plate such as anacrylic plate or a polycarbonate plate, a glass plate, or the like canbe used.

The optical member 240 illustrated in FIG. 4C includes theanti-reflection member 291, an anti-reflection member 293, and thesupport member 292. A layer that is positioned closest to the displaypanel is the anti-reflection member 293, and a layer that is positionedfarthest from the display panel is the anti-reflection member 291.

When an AR film is used for the anti-reflection member 291, thereflection of external light from a surface of the display device can bereduced. Alternatively, when an AG film is used for the anti-reflectionmember 291, reflection of surroundings of the display device on thesurface of the display device can be suppressed.

There is air between the optical member 240 and the display panels. Whenan AR film is used for the anti-reflection member 293, the reflection oflight between the optical member 240 and the air can be suppressed.

Alternatively, when an AG film is used for the anti-reflection member293, reflection of surroundings can be suppressed, and a user of thedisplay device can see display easily.

FIG. 4D illustrates an example in which a circularly polarizing plate295 is used as the optical member 240.

The circularly polarizing plate 295 includes a linear polarizing plateand a retardation plate. The linear polarizing plate includes, forexample, a linear polarizing layer between a pair of substrates. As anexample of a retardation plate, a quarter-wave plate or the like can begiven. The linear polarizing plate and the retardation plate areattached to each other by a bonding layer.

With the use of the circularly polarizing plate, a user of the displaydevice can be prevented from noticing an overlapping area because of thereflection of light from surfaces of the display panels and in thedisplay panels.

As illustrated in FIG. 4D, the circularly polarizing plate 295preferably overlaps with a plurality of display panels. This structurecan prevent a user of the display device from noticing a seam betweendisplay regions because of the reflection of light from a side surfaceof the display panel (see a portion surrounded by a dotted line in FIG.4D).

When the circularly polarizing plate is used as the optical member 240,a highly optically isotropic substrate is preferably used as substratesincluded in the display panels.

FIG. 4D illustrates an example in which a lower display panel includes asubstrate 202 a and a substrate 212 a that are highly opticallyisotropic and an upper display panel includes a substrate 202 b and asubstrate 212 b that are highly optically isotropic. A region 155 aincluding a display element and a region 156 a including a wiringelectrically connected to the display element are provided between thesubstrates 202 a and 212 a. Similarly, a region 155 b including adisplay element and a region 156 b including a wiring electricallyconnected to the display element are provided between the substrates 202b and 212 b.

A highly optically isotropic substrate has a low birefringence (in otherwords, a small amount of birefringence).

The absolute value of a retardation (phase difference) of a highlyoptically isotropic substrate is preferably less than or equal to 30 nm,further preferably less than or equal to 20 nm, still further preferablyless than or equal to 10 nm.

Examples of a highly optically isotropic film include a triacetylcellulose (TAC, also referred to as cellulose triacetate) film, acycloolefin polymer (COP) film, a cycloolefin copolymer (COC) film, andan acrylic film.

The optical member 240 illustrated in FIG. 4E includes the circularlypolarizing plate 295 and the support member 292. Either the supportmember 292 or the circularly polarizing plate 295 may be closer to thedisplay panel. When the support member 292 is arranged closer to thedisplay panel than the circularly polarizing plate 295 is, the supportmember 292 is preferably highly optically isotropic. When the circularlypolarizing plate 295 is arranged closer to the display panel than thesupport member 292 is, the support member 292 does not necessarily needto be optically isotropic; thus, the range of choices for the materialthat can be used for the support member 292 is widened.

The optical member 240 illustrated in each of FIGS. 4F and 4G includesthe circularly polarizing plate 295, an anti-reflection member 296, andthe support member 292. In the optical member 240 illustrated in FIG.4F, a layer that is positioned closest to the display panel is thesupport member 292, and a layer that is positioned farthest from thedisplay panel is the anti-reflection member 296. In the optical member240 illustrated in FIG. 4G, a layer that is positioned closest to thedisplay panel is the circularly polarizing plate 295, and a layer thatis positioned farthest from the display panel is the anti-reflectionmember 296.

An AR film is preferably used for the anti-reflection member 296. Withthis film, the reflection of external light from a surface of thedisplay device can be reduced.

Structural Example 2 of Display Panel

FIG. 5A is a top view of the display panel 100. FIG. 5B is an enlargedview of a region N surrounded by a dotted line in FIG. 5A.

The display panel 100 includes the display region 101 and the region102. The region 102 includes the region 110 transmitting visible lightand the region 120 blocking visible light. The region 110 transmittingvisible light and the region 120 blocking visible light are eachadjacent to the display region 101. In the display panel 100 in FIG. 5A,the region 110 transmitting visible light is provided along two sides ofthe display region 101. The width W of the region 110 transmittingvisible light along one side of the display region 101 may be the sameas or different from the width W of the region 110 transmitting visiblelight along the other side. FIG. 5A illustrates an example in which thewidths are the same.

When the heat resistance of the substrate is low, the substrate may bedeformed by heat in pressure bonding of an FPC. For example, a wiring isnot provided in a portion surrounded by a dotted line in FIG. 5B, andthus when a pressure bond head is in contact with the portion, creasesare likely to occur in the display panel. Therefore, as illustrated inFIG. 5C, a dummy wiring 121 is preferably formed near the region towhich an FPC is bonded with pressure. By arranging the dummy wiring 121in the region with which the pressure bond head is in contact,generation of creases on the display panel can be suppressed. The dummywiring 121 is preferably formed using the same material and in the samestep as those of the conductive layer included in the display panel.Thus, an increase in the number of fabrication steps due to theformation of the dummy wiring 121 can be prevented.

Structure Example 3 of Display Device

FIGS. 5D and 5E are perspective views of the display device 12 differentfrom that in FIG. 2A. The display device 12 in FIGS. 5D and 5E includesfour display panels 100 illustrated in FIG. 5A arranged in a 2×2 matrix(two display panels in the longitudinal direction and the lateraldirection). FIG. 5D is a perspective view of the display device 12 onthe display surface side. FIG. 5E is a perspective view of the displaydevice 12 on the side opposite to the display surface side.

FIGS. 5D and 5E illustrate examples where each of the display panels iselectrically connected to an FPC.

The display device 12 illustrated in FIGS. 5D and 5E includes thedisplay panel 100 a, the display panel 100 b, the display panel 100 c,and a display panel 100 d.

In FIGS. 5D and 5E, short sides of the display panels 100 a and 100 boverlap with each other such that part of the display region 101 a andpart of the region 110 b transmitting visible light overlap with eachother. Furthermore, long sides of the display panels 100 a and 100 coverlap with each other such that part of the display region 101 a andpart of the region 110 c transmitting visible light overlap with eachother.

In FIGS. 5D and 5E, part of the display region 101 b overlaps with partof the region 110 c transmitting visible light and part of a region 110d transmitting visible light. In addition, part of the display region101 c overlaps with part of the region 110 d transmitting visible light.

Thus, as illustrated in FIG. 5D, a region where the display region 101a, the display region 101 b, the display region 101 c, and a displayregion 101 d are placed seamlessly can serve as the display region 13 ofthe display device 12.

In the center portion of the display device 12, the display panel 100 bis stacked over the display panel 100 a, the display panel 100 c isstacked over the display panel 100 b, and the display panel 100 d isstacked over the display panel 100 c.

Here, it is preferable that the display panel 100 have flexibility. Forexample, a pair of substrates included in the display panel 100preferably have flexibility.

Thus, as illustrated in FIGS. 5D and 5E, a region near the FPC 112 a ofthe display panel 100 a can be bent so that part of the display panel100 a and part of the FPC 112 a can be placed under the display region101 b of the display panel 100 b adjacent to the FPC 112 a. As a result,the FPC 112 a can be placed without physical interference with the rearsurface of the display panel 100 b. Furthermore, when the display panel100 a and the display panel 100 b overlap with each other and are fixed,it is not necessary to consider the thickness of the FPC 112 a; thus,the top surface of the region 110 b transmitting visible light and thetop surface of the display panel 100 a can be substantially leveled.This can make an end portion of the display panel 100 b over the displayregion 101 a less noticeable.

Moreover, each display panel 100 is made flexible, in which case thedisplay panel 100 b can be curved gently so that the top surface of thedisplay region 101 b of the display panel 100 b and the top surface ofthe display region 101 a of the display panel 100 a are leveled. Thus,the display regions can be leveled except the vicinity of a region wherethe display panel 100 a and the display panel 100 b overlap with eachother, so that the display quality of an image displayed on the displayregion 13 of the display device 12 can be improved.

Although the relation between the display panel 100 a and the displaypanel 100 b is taken as an example in the above description, the samecan apply to the relation between any other two adjacent display panels.

FIGS. 6A to 6E and FIGS. 7A to 7D are examples of cross-sectional viewsof the two display panels attached to each other.

In FIGS. 6A to 6E, a lower display panel includes the display region 101a, a region 110 a transmitting visible light, and the region 120 ablocking visible light. The lower display panel is electricallyconnected to the FPC 112 a. An upper display panel (display panel on thedisplay surface side) includes the display region 101 b, the region 110b transmitting visible light, and the region 120 b that blocking visiblelight. The upper display panel is electrically connected to an FPC 112b.

In FIG. 6A, the FPC 112 a and the FPC 112 b are connected to the displaysurface side (front surface side) of the lower display panel and thedisplay surface side of the upper display panel, respectively.

FIG. 6B illustrates an example in which two display panels are partlyattached to each other with the above-described light-transmitting layer103. FIG. 6B illustrates an example in which the width of the region 110b transmitting visible light is the same as that of thelight-transmitting layer 103.

FIG. 6C illustrates an example in which the FPC 112 a and the FPC 112 bare connected to the side (rear surface side) opposite to the displaysurface of the lower display panel and the side (rear surface side)opposite to the display surface of the upper display panel,respectively.

In FIG. 6C, the light-transmitting layer 103 is provided between theregion 120 a blocking visible light of the lower display panel and thedisplay region 101 b of the upper display panel.

When an FPC is connected to the rear surface side of a lower displaypanel, an end portion of the lower display panel can be attached to therear surface of an upper display panel; thus, the attachment area can beincreased and the mechanical strength of the attached portion can beincreased.

In FIG. 6D, the light-transmitting layer 103 overlaps with a region ofthe display region 101 a not overlapping with the upper display panel.Furthermore, the region 110 a transmitting visible light and thelight-transmitting layer 103 overlap with each other.

Fine dirt such as dust in the air might be attached depending on amaterial of the light-transmitting layer. In such a case, it ispreferable that the region of the display region 101 a not overlappingwith the upper display panel not overlap with the light-transmittinglayer 103. This makes it possible to suppress unclear display of thedisplay device due to dirt or the like attached to thelight-transmitting layer 103.

In FIG. 6E, the light-transmitting layer 103 overlaps with a region ofthe upper display panel not overlapping with the display region 101 a.

In the structure illustrated in FIG. 6E, the light-transmitting layer isnot provided on the outermost surface of the display surface of thedisplay device; thus, unclear display of the display device due to dirtor the like attached to the light-transmitting layer 103 can beprevented. In addition, when a light-transmitting layer havingattachability is provided on the rear surface of the display device, thedisplay device can be detachably attached to a desired portion with theuse of a surface of the light-transmitting layer that is not in contactwith the display panel.

In FIG. 7A, a resin layer 131 covers front surfaces of the display panel100 a and the display panel 100 b. The resin layer 131 is preferablyprovided to cover the display regions of the display panels 100 a and100 b and a region where the display panel 100 a overlaps with thedisplay panel 100 b.

Providing the resin layer 131 over these display panels 100 can increasethe mechanical strength of the display device 12. In addition, the resinlayer 131 is formed to have a flat surface, whereby the display qualityof an image displayed on the display region 13 can be increased. Forexample, when a coating apparatus such as a slit coater, a curtaincoater, a gravure coater, a roll coater, or a spin coater is used, theresin layer 131 with high flatness can be formed.

The refractive index of the resin layer 131 is preferably 0.8 to 1.2times, further preferably 0.9 to 1.1 times, and still further preferably0.95 to 1.15 times as high as the refractive index of the substrate onthe display surface side of the display panel 100. Light can beextracted outside more efficiently as the difference in refractive indexbetween the display panel 100 and the resin layer 131 becomes smaller.In addition, the resin layer 131 with such a refractive index isprovided to cover a step portion between the display panel 100 a and thedisplay panel 100 b, whereby the step portion is not easily noticed, andthe display quality of an image displayed on the display region 13 canbe increased.

The resin layer 131 transmits visible light. For the resin layer 131,for example, an organic resin such as an epoxy resin, an aramid resin,an acrylic resin, a polyimide resin, a polyamide resin, or apolyamide-imide resin can be used.

Alternatively, as illustrated in FIG. 7B, a protective substrate 132 ispreferably provided over the display device 12 with the resin layer 131provided therebetween. In that case, the resin layer 131 may serve as abonding layer for bonding the protective substrate 132 to the displaydevice 12.

With the protective substrate 132, the surface of the display device 12can be protected, and moreover, the mechanical strength of the displaydevice 12 can be increased. For the protective substrate 132, alight-transmitting material is used at least in a region overlappingwith the display region 13. Furthermore, the protective substrate 132may have a light-blocking property in a region other than the regionoverlapping with the display region 13 so as not to be noticed.

The protective substrate 132 may function as a touch panel. In the casewhere the display panel 100 is flexible and capable of being bent, theprotective substrate 132 is also preferably flexible.

Furthermore, a difference in refractive index between the protectivesubstrate 132 and the substrate on the display surface side of thedisplay panel 100 or the resin layer 131 is preferably less than orequal to 20%, further preferably less than or equal to 10%, and stillfurther preferably less than or equal to 5%.

As the protective substrate 132, a plastic substrate that is formed as afilm can be used. For the plastic substrate, a polyester resin such aspolyethylene terephthalate (PET) or polyethylene naphthalate (PEN), apolyacrylonitrile resin, a polyimide resin, a polymethyl methacrylateresin, a polycarbonate (PC) resin, a polyethersulfone (PES) resin, apolyamide resin (e.g., nylon or aramid), a polycycloolefin resin, apolystyrene resin, a polyamide imide resin, a polyvinyl chloride resin,a polyetheretherketone (PEEK) resin, a polysulfone (PSF) resin, apolyetherimide (PEI) resin, a polyarylate (PAR) resin, a polybutyleneterephthalate (PBT) resin, a polytetrafluoroethylene (PTFE) resin, asilicone resin, or the like can be used. Alternatively, a substrate inwhich a fibrous body is impregnated with a resin (also referred to asprepreg) or a substrate whose coefficient of linear expansion is reducedby mixing an organic resin with an inorganic filler can be used. Theprotective substrate 132 is not limited to the resin film, and atransparent nonwoven fabric formed by processing pulp into a continuoussheet, a sheet including an artificial spider's thread fiber containingprotein called fibroin, a complex in which the transparent nonwovenfabric or the sheet and a resin are mixed, a stack of a resin film and anonwoven fabric containing a cellulose fiber whose fiber width is 4 nmor more and 100 nm or less, or a stack of a resin film and a sheetincluding an artificial spider's thread fiber may be used.

Note that the display device or the display panel of one embodiment ofthe present invention may be attached to an acrylic plate, a glassplate, a wooden plate, a metal plate, or the like. The display surfaceof the display device or that of the display panel or the surfaceopposite to the display surface thereof may be attached to these plates(in the case where the display surface is attached to any of theseplates, a plate that transmits visible light is used). It is preferablethat the display device or the display panel be detachably attached toany of these plates.

As the protective substrate 132, at least one of a polarizing plate, acircular polarizing plate, a retardation plate, an optical film, and thelike can be used. The above-described optical member 240 can be used forthe protective substrate 132.

It is preferable that not only the display panel but also a plate behardly deformed by a temperature change in the case where a state inwhich the display panel is attached to the plate is held. For example,the coefficient of thermal expansion of the plate is preferably lowerthan or equal to 60 ppm/° C., further preferably lower than or equal to30 ppm/° C. For example, a metal plate such as an aluminum plate or aglass epoxy plate can be favorably used.

As illustrated in FIG. 7C, a resin layer 133 and a protective substrate134 can be provided on surfaces opposite to the display surfaces of thedisplay panels 100 a and 100 b. Providing a substrate supporting thedisplay panels on the rear surfaces of the display panels can suppressunintended warping or bending of the display panels, whereby the displaysurfaces can be kept smooth. Thus, the display quality of an imagedisplayed on the display region 13 can be improved.

Note that the resin layer 133 and the protective substrate 134, whichare provided on the sides opposite to the display surfaces, do notnecessarily have light transmittance, and a material that absorbs orreflects visible light may be used.

As illustrated in FIG. 7D, the resin layer 131 and the protectivesubstrate 132 can be provided on the front surfaces of the displaypanels, and the resin layer 133 and the protective substrate 134 may beprovided on the rear surfaces thereof. In this manner, the displaypanels 100 a and 100 b are sandwiched between the two protectivesubstrates, whereby the mechanical strength of the display device 12 canbe further increased.

It is preferable that the total thickness of the resin layer 131 and theprotective substrate 132 be approximately the same as that of the resinlayer 133 and the protective substrate 134. For example, it ispreferable that the thicknesses of the resin layers 131 and 133 be madesubstantially equal to each other, and materials having the samethickness be used for the protective substrates 132 and 134. In thatcase, the display panels 100 can be located at the center of the stackin the thickness direction. For example, when the stack including thedisplay panels 100 at the center in the thickness direction is bent,stress in the lateral direction applied to the display panels 100 bybending can be relieved, which prevents the display panels 100 frombeing damaged.

In the case where the thicknesses of the resin layer and the protectivesubstrate differ between an end portion and a center portion of thedisplay device, for example, the total thickness of the resin layer 131and the protective substrate 132 and that of the resin layer 133 and theprotective substrate 134 are preferably compared under the samecondition that is appropriately selected from conditions such as theaverage thickness, the largest thickness, the smallest thickness, andthe like.

In FIG. 7D, the same material is preferably used for the resin layers131 and 133 because the manufacturing cost can be reduced. Similarly,the same material is preferably used for the protective substrates 132and 134 because the manufacturing cost can be reduced.

As illustrated in FIGS. 7C and 7D, an opening for leading the FPC 112 ais preferably provided in the resin layer 133 and the protectivesubstrate 134, which are located on the rear surface sides of thedisplay panels 100 a and 100 b. In particular, when the resin layer 133is provided to cover part of the FPC 112 a as illustrated in FIG. 7D,the mechanical strength at a connection portion between the displaypanel 100 a and the FPC 112 a can be increased, and defects such asseparation of the FPC 112 a can be suppressed. Similarly, the resinlayer 133 is preferably provided to cover part of the FPC 112 b.

Next, a structure example of the display panel 100 is described. FIG. 8Ais an example of a top view in which a region P in FIG. 5A is enlarged,and FIG. 8B is an example of a top view in which a region Q in FIG. 5Ais enlarged.

As illustrated in FIG. 8A, in the display region 101, a plurality ofpixels 141 are arranged in matrix. In the case where the display panel100 capable of full color display with three colors of red, blue, andgreen is formed, each of the pixels 141 corresponds to a sub-pixelcapable of displaying any of the three colors. A sub-pixel capable ofdisplaying white or yellow may be provided in addition to the sub-pixelscapable of displaying any of the three colors. A region including thepixels 141 corresponds to the display region 101.

A wiring 142 a and a wiring 142 b are electrically connected to eachpixel 141. The wirings 142 a each intersect with the wiring 142 b, andare electrically connected to a circuit 143 a. The wirings 142 b areelectrically connected to a circuit 143 b. One of the circuits 143 a and143 b can function as a scan line driver circuit, and the other canfunction as a signal line driver circuit. One or both of the circuits143 a and 143 b are not necessarily provided.

In FIG. 8A, a plurality of wirings 145 electrically connected to thecircuit 143 a or the circuit 143 b are provided. The wiring 145 iselectrically connected to an FPC 123 in an unillustrated region and hasa function of supplying a signal from the outside to the circuits 143 aand 143 b.

In FIG. 8A, a region including the circuit 143 a, the circuit 143 b, theplurality of wirings 145, and the like corresponds to the region 120blocking visible light.

In FIG. 8B, a region outside the pixel 141 provided closest to the endcorresponds to the region 110 transmitting visible light. The region 110transmitting visible light does not include members that blocks visiblelight, such as the pixel 141, the wiring 142 a, and the wiring 142 b.Note that in the case where part of the pixel 141, the wiring 142 a, orthe wiring 142 b transmits visible light, the part of the pixel 141, thewiring 142 a, or the wiring 142 b may be provided to extend to theregion 110 transmitting visible light.

In the case where the width of the region 110 transmitting visible lightis different between the display panels, or in the case where the widthvaries depending on the position in one display panel, the shortestlength can be referred to as the width W. In FIG. 8B, the distancebetween the pixel 141 and the end portion of the substrate (that is, thewidth W of the region 110 transmitting visible light) in the verticaldirection is the same as that in the horizontal direction, but oneembodiment of the present invention is not limited thereto.

FIG. 8C is a cross-sectional view taken along line A1-A2 in FIG. 8B. Thedisplay panel 100 includes a pair of substrates (a substrate 151 and asubstrate 152) that transmit visible light. The substrate 151 and thesubstrate 152 are bonded to each other with a bonding layer 154. Here,the substrate on which the pixel 141, the wiring 142 b, and the like areformed is referred to as the substrate 151.

As illustrated in FIGS. 8B and 8C, in the case where the pixel 141 ispositioned closest to the end of the display region 101, the width ofthe region 110 transmitting visible light is the distance between theend portion of the substrate 151 or the substrate 152 and the endportion of the pixel 141.

Note that the end portion of the pixel 141 refers to the end portion ofthe member that is positioned closest to the end and blocks visiblelight in the pixel 141. Alternatively, in the case where alight-emitting element including a layer containing a light-emittingorganic compound between a pair of electrodes (also referred to as anorganic EL element) is used as the pixel 141, the end portion of thepixel 141 may be any of the end portion of the lower electrode, the endportion of the layer containing a light-emitting organic compound, andthe end portion of the upper electrode.

FIG. 9A is an example of a top view in which the region Q is enlarged;the position of the wiring 142 a is different from that in FIG. 8B. FIG.9B is a cross-sectional view taken along line B1-B2 in FIG. 9A, and FIG.9C is a cross-sectional view taken along line C1-C2 in FIG. 9A.

As illustrated in FIGS. 9A to 9C, in the case where the wiring 142 a ispositioned closest to the end of the display region 101, the width W ofthe region 110 transmitting visible light is the distance between theend portion of the substrate 151 or the substrate 152 and the endportion of the wiring 142 a. In the case where the wiring 142 atransmits visible light, the region 110 transmitting visible light mayinclude a region where the wiring 142 a is provided.

Structure Example of Light-Emitting Element

FIGS. 10A and 10B illustrate structure examples of the light-emittingelement included in the display panel.

For example, the display panel includes a first light-emitting element1105R, a second light-emitting element 1105G, and a third light-emittingelement 1105B that are illustrated in FIG. 10A or 10B. The display panelmay further include a color filter 1104R, a color filter 1104G, and acolor filter 1104B that are illustrated in FIG. 10B.

In FIG. 10A, the first light-emitting element 1105R includes a firstelectrode 1101, an EL layer 1103R, and a second electrode 1102. Thesecond light-emitting element 1105G includes the first electrode 1101,an EL layer 1103G, and the second electrode 1102. The thirdlight-emitting element 1105B includes the first electrode 1101, and anEL layer 1103B, and the second electrode 1102. Note that the EL layersincluded in the three light-emitting elements contain differentmaterials partly or entirely and are formed by a separate coloringmethod. This means that, for example, the EL layer 1103R can be an ELlayer that emits red light, the EL layer 1103G can be an EL layer thatemits green light, and the EL layer 1103B can be an EL layer that emitsblue light.

At least one of the electrodes (in the case of FIG. 10A, the secondelectrode 1102 positioned in the arrow direction in which light isemitted from the EL layer) included in each of the light-emittingelements is preferably formed using a light-transmitting conductivematerial. In FIG. 10B, the first light-emitting element 1105R, thesecond light-emitting element 1105G, and the third light-emittingelement 1105B each include the first electrode 1101, an EL layer 1103,and the second electrode 1102. The color filter 1104R is provided in aregion overlapping with the first light-emitting element 1105R. Thecolor filter 1104G is provided in a region overlapping with the secondlight-emitting element 1105G. The color filter 1104B is provided in aregion overlapping with the third light-emitting element 1105B. Notethat the light-emitting elements share the same EL layer 1103.

The second electrode 1102 included in each of the light-emittingelements illustrated in FIG. 10B is preferably formed using alight-transmitting conductive material. Accordingly, red light 1106R oflight emitted from the EL layer 1103 can be extracted from the firstlight-emitting element 1105R to the outside through the color filter1104R. Furthermore, green light 1106G of the light emitted from the ELlayer 1103 can be extracted from the second light-emitting element 1105Gto the outside through the color filter 1104G. In addition, blue light1106B of the light emitted from the EL layer 1103 can be extracted fromthe third light-emitting element 1105B to the outside through the colorfilter 1104B. This means that the color filter 1104R has a function oftransmitting red light, the color filter 1104G has a function oftransmitting green light, and the color filter 1104B has a function oftransmitting blue light.

Although not illustrated in FIGS. 10A and 10B, each of the firstlight-emitting element 1105R, the second light-emitting element 1105G,and the third light-emitting element 1105B may be electrically connectedto a transistor that controls light emission.

The EL layers illustrated in FIGS. 10A and 10B each include functionallayers such as a light-emitting layer containing a light-emittingsubstance, a hole-injection layer, a hole-transport layer, anelectron-transport layer, and an electron-injection layer. In the caseof stacked EL layers, a charge generation layer is positioned betweenthe EL layers.

The light-emitting layers included in the EL layers illustrated in FIGS.10A and 10B can contain one or more kinds of organic compounds inaddition to the light-emitting substance. Light-emitting substances ofdifferent colors may be mixed in one light-emitting layer.Alternatively, light-emitting substances of different colors may becontained in the stacked light-emitting layers. In the case where thelight-emitting elements illustrated in FIGS. 10A and 10B each include aplurality of EL layers, a charge generation layer is provided betweenthe EL layers as described above. In that case, the EL layers preferablyemit light with different colors.

The first light-emitting element 1105R, the second light-emittingelement 1105G, and the third light-emitting element 1105B illustrated inFIG. 10B share the EL layer 1103. In that case, light with differentcolors can be obtained from the light-emitting elements while the ELlayer 1103 emits white light.

In the case where light emitted from the EL layer 1103 is white lightobtained by mixing light with a plurality of wavelengths are mixed asillustrated in FIG. 10B, it is preferable to employ a microcavitystructure by using the first electrode 1101 as a reflective electrodeand the second electrode 1102 as a transflective electrode to intensifylight with a specific wavelength. Note that a microcavity structure maybe employed also in the case where the EL layers are separately formedfor each light-emitting element as illustrated in FIG. 10A.

Since the first light-emitting element 1105R illustrated in FIG. 10A orFIG. 10B is a light-emitting element that emits red light, the thicknessof the first electrode 1101 is preferably adjusted so that an opticalpath length between the first electrode 1101 and the second electrode1102 may be set to an optical path length that increases the emissionintensity of red light. Furthermore, since the second light-emittingelement 1105G is a light-emitting element that emits green light, thethickness of the first electrode 1101 is preferably adjusted so that anoptical path length between the first electrode 1101 and the secondelectrode 1102 may be set to an optical path length that increases theemission intensity of green light. In addition, since the thirdlight-emitting element 1105B is a light-emitting element that emits bluelight, the thickness of the first electrode 1101 is preferably adjustedso that an optical path length between the first electrode 1101 and thesecond electrode 1102 may be set to an optical path length thatincreases the emission intensity of blue light.

In the case where light emitted from the EL layer 1103 is white light asillustrated in FIG. 10B, it is desirable that red light, green light,and blue light that constitute white light have independent emissionspectra that do not overlap with each other to prevent a reduction incolor purity. The emission spectrum of green light and the emissionspectrum of red light are especially likely to overlap with each otherbecause their peak wavelengths are close to each other. Thelight-emitting substances contained in the EL layer and thestacked-layer structure of the EL layer are important in preventing suchoverlap of the emission spectra. Although the number of steps can besmaller in the case of a display panel including a common EL layer thanin the case of a display panel including separately formed EL layers, itis difficult to select the light-emitting substances and design thestacked-layer structure of the EL layer such that overlap of differentemission spectra is prevented. One embodiment of the present inventioncan provide not only a display panel having favorable chromaticity foreach emission color, but also a display panel in which overlap ofdifferent emission spectra is prevented and chromaticity for eachemission color is favorable particularly when a common light-emittinglayer that emits white light is included.

The display panel described in this embodiment includes a plurality oflight-emitting elements and can display a full-color image. At present,some standards are established as quality indicators for full-colordisplays.

For example, the sRGB standard, which is an international standard forcolor spaces defined by the International Electrotechnical Commission(IEC) to standardize color reproduction on devices such as displays,printers, digital cameras, and scanners, is widely used. Note that inthe sRGB standard, the chromaticities (x, y) on the CIE 1931chromaticity coordinates (x,y chromaticity coordinates) defined by theInternational Commission on Illumination (CIE) are (0.640, 0.330) forred (R), (0.300, 0.600) for green (G), and (0.150, 0.060) for blue (B).

In the NTSC standard, which is a color gamut standard for analogtelevision systems defined by the National Television System Committee(NTSC) in America, the chromaticities (x, y) are (0.670, 0.330) for red(R), (0.210, 0.710) for green (G), and (0.140, 0.080) for blue (B).

In the DCI-P3 standard (defined by Digital Cinema Initiatives, LLC),which is the international unified standard used when distributingdigital movies (cinema), the chromaticities (x, y) are (0.680, 0.320)for red (R), (0.265, 0.690) for green (G), and (0.150, 0.060) for blue(B).

In Recommendation ITU-R BT.2020 (hereinafter referred to as BT.2020) forultra high definition television (UHDTV, also referred to as SuperHi-Vision), which is the standard defined by Japan BroadcastingCorporation (NHK), the chromaticities (x, y) are (0.708, 0.292) for red,(0.170, 0.797) for green, and (0.131, 0.046) for blue.

As described above, a variety of standards for displays are defined. Thedisplay panel of one embodiment of the present invention includeslight-emitting elements (a light-emitting element that emits red light,a light-emitting element that emits green light, and a light-emittingelement that emits blue light) that emit light whose chromaticities fallwithin the chromaticity ranges (a region A, a region B, and a region C)represented by color coordinates in FIG. 11. Specifically, the displaypanel includes at least the first light-emitting element 1105R fromwhich the red light 1106R can be obtained, the second light-emittingelement 1105G from which the green light 1106G can be obtained, and thethird light-emitting element 1105B from which the blue light 1106B canbe obtained. Light obtained from the first light-emitting element 1105Rhas chromaticity that falls within the region A in the color coordinatesin FIG. 11, i.e., a CIE 1931 chromaticity coordinate x of greater than0.680 and less than or equal to 0.720 and a CIE 1931 chromaticitycoordinate y of greater than or equal to 0.260 and less than or equal to0.320. Light obtained from the second light-emitting element 1105G haschromaticity that falls within the region B in the color coordinates inFIG. 11, i.e., a CIE 1931 chromaticity coordinate x of greater than orequal to 0.130 and less than or equal to 0.250 and a CIE 1931chromaticity coordinate y of greater than 0.710 and less than or equalto 0.810. Light obtained from the third light-emitting element 1105B haschromaticity that falls within the region C in the color coordinates inFIG. 11, i.e., a CIE 1931 chromaticity coordinate x of greater than orequal to 0.120 and less than or equal to 0.170 and a CIE 1931chromaticity coordinate y of greater than or equal to 0.020 and lessthan 0.060. Note that as illustrated in FIG. 10B, a structure in whichthe light-emitting elements and the color filters are used incombination and light emissions obtained from the light-emittingelements through the color filters have chromaticities that fall withinin the above chromaticity ranges may be employed. A display panelincluding such light-emitting elements can provide high-qualityfull-color displays. It is needless to say that a structure thatachieves the chromaticities that fall within the above chromaticityranges without using color filters may be employed as illustrated inFIG. 10A.

Note that the peak wavelength of the emission spectrum of the firstlight-emitting element 1105R illustrated in FIG. 10A is preferablygreater than or equal to 620 nm and less than or equal to 680 nm. Thepeak wavelength of the emission spectrum of the second light-emittingelement 1105G illustrated in FIG. 10A is preferably greater than orequal to 500 nm and less than or equal to 530 nm. The peak wavelength ofthe emission spectrum of the third light-emitting element 1105Billustrated in FIG. 10A is preferably greater than or equal to 430 nmand less than or equal to 460 nm. The half widths of the emissionspectra of the first light-emitting element 1105R, the secondlight-emitting element 1105G, and the third light-emitting element 1105Bare preferably greater than or equal to 5 nm and less than or equal to45 nm, greater than or equal to 5 nm and less than or equal to 35 nm,and greater than or equal to 5 nm and less than or equal to 25 nm,respectively. The peak wavelengths and the half widths of emissionspectra of light passed through the color filters illustrated in FIG.10B preferably have similar values.

In one embodiment of the present invention, the above chromaticities arepreferably obtained so that the area ratio with respect to the BT.2020color gamut in the CIE chromaticity coordinates (x, y) can become higherthan or equal to 80%, further preferably higher than or equal to 90%, orthe color gamut coverage can become higher than or equal to 75%, furtherpreferably higher than or equal to 85%.

The chromaticities may be measured with any of a luminance colorimeter,a spectroradiometer, and an emission spectrometer, and it is sufficientthat the above-described chromaticities be met in any one of themeasurements. Note that it is preferable that the above-describedchromaticities be met in all of the measurements.

In one embodiment of the present invention, the same material is usedfor the layer that constitutes the hole-transport layer and that is incontact with the hole-injection layer in each of the light-emittingelements for different colors. For example, the hole-transport layer inthe light-emitting element emitting red light and that in thelight-emitting element emitting green light each include a firsthole-transport layer that is in contact with the hole-injection layerand a second hole-transport layer that is in contact with thelight-emitting layer. The hole-transport layer in the light-emittingelement emitting blue light includes only the first hole-transport layerthat is in contact with both the hole-injection layer and thelight-emitting layer.

Note that in an element emitting blue fluorescence, the HOMO level andthe LUMO level of a host material in a light-emitting layer are deep.Depending on the material for a hole-injection layer, the HOMO level ofa hole-transport layer often needs to be shallow so that electrons canbe extracted from the hole-injection layer. In that case, thehole-transport layer needs to have a structure in which a layer with ashallow HOMO level and a layer with a deep HOMO level are sequentiallystacked. In one embodiment of the present invention, a mixed layer of ahole-transport material and a metal oxide is used as the hole-injectionlayer. Use of a hole-transport material with a deep HOMO level for themixed layer allows the hole-transport layer to be formed using ahole-transport material with a deep HOMO level. Accordingly, even whenthe hole-transport layer has a single-layer structure, holes can beinjected into the light-emitting layer emitting blue fluorescence.

In each of the light-emitting elements for different colors, thehole-injection layer and the first hole-transport layer preferablycontain the same hole-transport material.

In each of the light-emitting element emitting red light and thelight-emitting element emitting green light, the second hole-transportlayer can be used as a layer for adjusting the optical path length. Thematerial used for the second hole-transport layer preferably has ashallower HOMO level than that used for the first hole-transport layer.In this manner, power consumption by the light-emitting element emittingred light and the light-emitting element emitting green light can bereduced. It is preferable that the material contained in the secondhole-transport layer be also contained in the light-emitting layer ofthe light-emitting element emitting red light and the light-emittinglayer of the light-emitting element emitting green light.

As described above, the display device of one embodiment of the presentinvention can display an image with a wide color gamut and can have awide display region in which a seam is less likely to be noticed.

This embodiment can be combined with any of other embodiments asappropriate. In the case where a plurality of structure examples aredescribed in one embodiment in this specification, some of the structureexamples can be combined as appropriate.

Embodiment 2

In this embodiment, a light-emitting element and a light-emitting panelthat can be used for the display device of one embodiment of the presentinvention are described with reference to FIGS. 12A to 12D and FIGS. 13Aand 13B.

<<Basic Structure of Light-Emitting Element>>

A basic structure of a light-emitting element will be described. FIG.12A illustrates a light-emitting element including, between a pair ofelectrodes, an EL layer. Specifically, an EL layer 1203 is providedbetween a first electrode 1201 and a second electrode 1202 (singlestructure). The EL layer 1203 includes at least a light-emitting layer.

The light-emitting element may include a plurality of EL layers betweenthe pair of electrodes. FIG. 12B illustrates a light-emitting elementthat has a stacked-layer structure (tandem structure) in which two ELlayers (EL layers 1203 a and 1203 b) are provided between a pair ofelectrodes and a charge generation layer 1204 is provided between thetwo EL layers. With the use of such a tandem light-emitting element, alight-emitting panel which can be driven at low voltage with low powerconsumption can be obtained.

The charge generation layer 1204 has a function of injecting electronsinto one of the EL layers 1203 a and 1203 b and injecting holes into theother of the EL layers when voltage is applied between the firstelectrode 1201 and the second electrode 1202. Thus, when voltage isapplied to the first electrode 1201 in FIG. 12B such that the potentialof the first electrode 1201 becomes higher than that of the secondelectrode 1202, the charge generation layer 1204 injects electrons intothe EL layer 1203 a and injects holes into the EL layer 1203 b.

Note that in terms of light extraction efficiency, the charge generationlayer 1204 preferably transmits visible light (specifically, the visiblelight transmittance of the charge generation layer 1204 is preferably40% or higher). Furthermore, the charge generation layer 1204 functionseven if it has lower conductivity than the first electrode 1201 or thesecond electrode 1202.

FIG. 12C illustrates a stacked-layer structure of the EL layer 1203. Inthis case, the first electrode 1201 is regarded as functioning as ananode. The EL layer 1203 has a structure in which a hole-injection layer1211, a hole-transport layer 1212, a light-emitting layer 1213, anelectron-transport layer 1214, and an electron-injection layer 1215 arestacked in this order over the first electrode 1201. Even in the casewhere a plurality of EL layers are provided as in the tandem structureillustrated in FIG. 12B, the layers in each EL layer are sequentiallystacked from the anode side as described above. When the first electrode1201 is a cathode and the second electrode 1202 is an anode, thestacking order of the layers is reversed.

The light-emitting layer 1213 contains a light-emitting substance and aplurality of substances in appropriate combination, so that fluorescenceor phosphorescence of a desired emission color can be obtained. Thelight-emitting layer 1213 may have a stacked-layer structure havingdifferent emission colors. In that case, light-emitting substances andother substances are different between the stacked light-emittinglayers. Alternatively, the plurality of EL layers (the EL layers 1203 aand 1203 b) in FIG. 12B may exhibit their respective emission colors.Also in that case, light-emitting substances and other substances aredifferent between the light-emitting layers.

In the light-emitting element, for example, a micro optical resonator(microcavity) structure in which the first electrode 1201 is areflective electrode and the second electrode 1202 is a transflectiveelectrode can be employed in FIG. 12C, whereby light emission from thelight-emitting layer 1213 in the EL layer 1203 can be resonated betweenthe electrodes and light passing and exiting through the secondelectrode 1202 can be intensified.

Note that when the first electrode 1201 of the light-emitting element isa reflective electrode having a structure in which a reflectiveconductive material and a light-transmitting conductive material(transparent conductive film) are stacked, optical adjustment can beperformed by controlling the thickness of the transparent conductivefilm. Specifically, when the wavelength of light from the light-emittinglayer 1213 is λ, the distance between the first electrode 1201 and thesecond electrode 1202 is preferably adjusted to around mλ/2 (m is anatural number).

To amplify desired light (wavelength: λ) obtained from thelight-emitting layer 1213, the optical path length from the firstelectrode 1201 to a region where desired light is obtained in thelight-emitting layer 1213 (light-emitting region) and the optical pathlength from the second electrode 1202 to the region where desired lightis obtained in the light-emitting layer 1213 (light-emitting region) arepreferably adjusted to around (2m′+1)λ/4 (m′ is a natural number). Here,the light-emitting region means a region where holes and electrons arerecombined in the light-emitting layer 1213.

By such optical adjustment, the spectrum of specific monochromatic lightfrom the light-emitting layer 1213 can be narrowed and light emissionwith high color purity can be obtained.

In that case, the optical path length between the first electrode 1201and the second electrode 1202 is, to be exact, the total thickness froma reflective region in the first electrode 1201 to a reflective regionin the second electrode 1202. However, it is difficult to exactlydetermine the reflective regions in the first electrode 1201 and thesecond electrode 1202; thus, it is assumed that the above effect can besufficiently obtained wherever the reflective regions may be set in thefirst electrode 1201 and the second electrode 1202. Furthermore, theoptical path length between the first electrode 1201 and thelight-emitting layer emitting desired light is, to be exact, the opticalpath length between the reflective region in the first electrode 1201and the light-emitting region where desired light is obtained in thelight-emitting layer. However, it is difficult to precisely determinethe reflective region in the first electrode 1201 and the light-emittingregion where desired light is obtained in the light-emitting layer;thus, it is assumed that the above effect can be sufficiently obtainedwherever the reflective region and the light-emitting region may be setin the first electrode 1201 and the light-emitting layer emittingdesired light.

The light-emitting element in FIG. 12C has a microcavity structure, sothat light (monochromatic light) with different wavelengths can beextracted even if the same EL layer is used. Thus, separate coloring forobtaining a plurality of emission colors (e.g., R, G, and B) is notnecessary. Therefore, high resolution can be easily achieved. Note thata combination with coloring layers (color filters) is also possible.Furthermore, emission intensity of light with a specific wavelength inthe front direction can be increased, whereby power consumption can bereduced.

At least one of the first electrode 1201 and the second electrode 1202is a light-transmitting electrode (e.g., a transparent electrode or atransflective electrode). In the case where the light-transmittingelectrode is a transparent electrode, the transparent electrode has avisible light transmittance of higher than or equal to 40%. In the casewhere the light-transmitting electrode is a transflective electrode, thetransflective electrode has a visible light reflectance of higher thanor equal to 20% and lower than or equal to 80%, preferably higher thanor equal to 40% and lower than or equal to 70%. These electrodespreferably have a resistivity of 1×10⁻² 2 cm or less.

When the first electrode 1201 or the second electrode 1202 is areflective electrode, the visible light reflectance of the reflectiveelectrode is higher than or equal to 40% and lower than or equal to100%, preferably higher than or equal to 70% and lower than or equal to100%. This electrode preferably has a resistivity of 1×10⁻² 2 cm orless.

<Specific Structure and Fabrication Method of Light-Emitting Element>>

Specific structures and specific fabrication methods of light-emittingelements will be described. Here, a light-emitting element having thetandem structure in FIG. 12B and a microcavity structure will bedescribed with reference to FIG. 12D. In the light-emitting element inFIG. 12D, the first electrode 1201 is formed as a reflective electrodeand the second electrode 1202 is formed as a transflective electrode.Thus, a single-layer structure or a stacked-layer structure can beformed using one or more kinds of desired conductive materials. Notethat the second electrode 1202 is formed after formation of the EL layer1203 b, with the use of a material selected as described above. Forfabrication of these electrodes, a sputtering method or a vacuumevaporation method can be used.

<First Electrode and Second Electrode>

As materials used for the first electrode 1201 and the second electrode1202, any of the materials below can be used in an appropriatecombination as long as the functions of the electrodes described abovecan be fulfilled. For example, a metal, an alloy, an electricallyconductive compound, a mixture of these, and the like can beappropriately used. Specifically, an In—Sn oxide (also referred to asITO), an In—Si—Sn oxide (also referred to as ITSO), an In—Zn oxide, anIn—W—Zn oxide, or the like can be used. In addition, it is possible touse a metal such as aluminum (Al), titanium (Ti), chromium (Cr),manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu),gallium (Ga), zinc (Zn), indium (In), tin (Sn), molybdenum (Mo),tantalum (Ta), tungsten (W), palladium (Pd), gold (Au), platinum (Pt),silver (Ag), yttrium (Y), or neodymium (Nd) or an alloy containing anappropriate combination of any of these metals. It is also possible touse a Group 1 element or a Group 2 element in the periodic table, whichis not described above (e.g., lithium (Li), cesium (Cs), calcium (Ca),or strontium (Sr)), a rare earth metal such as europium (Eu) orytterbium (Yb), an alloy containing an appropriate combination of any ofthese elements, graphene, or the like.

In the light-emitting element in FIG. 12D, when the first electrode 1201is an anode, a hole-injection layer 1211 a and a hole-transport layer1212 a of the EL layer 1203 a are sequentially stacked over the firstelectrode 1201 by a vacuum evaporation method. After the EL layer 1203 aand the charge generation layer 1204 are formed, a hole-injection layer1211 b and a hole-transport layer 1212 b of the EL layer 1203 b aresequentially stacked over the charge generation layer 1204 in a similarmanner.

<Hole-Injection Layer and Hole-Transport Layer>

The hole-injection layers (1211, 1211 a, and 1211 b) inject holes fromthe first electrode 1201 that is an anode or the charge generation layer(1204) to the EL layers (1203, 1203 a, and 1203 b) and each contain amaterial with a high hole-injection property.

As examples of the material with a high hole-injection property,transition metal oxides such as molybdenum oxide, vanadium oxide,ruthenium oxide, tungsten oxide, and manganese oxide can be given.Alternatively, it is possible to use any of the following materials:phthalocyanine-based compounds such as phthalocyanine (abbreviation:H2Pc) and copper phthalocyanine (abbreviation: CuPc); aromatic aminecompounds such as4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation:DPAB) andN,N′-bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine(abbreviation: DNTPD); high molecular compounds such aspoly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid)(abbreviation: PEDOT/PSS); and the like.

Alternatively, as the material with a high hole-injection property, acomposite material containing a hole-transport material and an acceptormaterial (an electron-accepting material) can also be used. In thatcase, the acceptor material extracts electrons from a hole-transportmaterial, so that holes are generated in the hole-injection layers(1211, 1211 a, and 1211 b) and the holes are injected into thelight-emitting layers (1213, 1213 a, and 1213 b) through thehole-transport layers (1212, 1212 a, and 1212 b). Note that each of thehole-injection layers (1211, 1211 a, and 1211 b) may be formed to have asingle-layer structure using a composite material containing ahole-transport material and an acceptor material (electron-acceptingmaterial), or a stacked-layer structure in which a layer including ahole-transport material and a layer including an acceptor material(electron-accepting material) are stacked.

The hole-transport layers (1212, 1212 a, and 1212 b) transport theholes, which are injected from the first electrode 1201 by thehole-injection layers (1211, 1211 a, and 1211 b), to the light-emittinglayers (1213, 1213 a, and 1213 b). Note that the hole-transport layers(1212, 1212 a, and 1212 b) each contain a hole-transport material. It isparticularly preferable that the HOMO level of the hole-transportmaterial included in the hole-transport layers (1212, 1212 a, and 1212b) be the same as or close to that of the hole-injection layers (1211,1211 a, and 1211 b).

Examples of the acceptor material used for the hole-injection layers(1211 a and 1211 b) include an oxide of a metal belonging to any ofGroup 4 to Group 8 of the periodic table. As specific examples,molybdenum oxide, vanadium oxide, niobium oxide, tantalum oxide,chromium oxide, tungsten oxide, manganese oxide, and rhenium oxide canbe given. Among these, molybdenum oxide is especially preferable sinceit is stable in the air, has a low hygroscopic property, and is easy tohandle. Alternatively, organic acceptors such as a quinodimethanederivative, a chloranil derivative, and a hexaazatriphenylene derivativecan be used. Specifically,7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:F4-TCNQ), chloranil,2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation:HAT-CN), or the like can be used.

The hole-transport materials used for the hole-injection layers (1211,1211 a, and 1211 b) and the hole-transport layers (1212, 1212 a, and1212 b) are preferably substances with a hole mobility of greater thanor equal to 10⁻⁶ cm²/Vs. Note that other substances may be used as longas the substances have a hole-transport property higher than anelectron-transport property.

Preferred hole-transport materials are π-electron rich heteroaromaticcompounds (e.g., carbazole derivatives and indole derivatives) andaromatic amine compounds, examples of which include compounds having anaromatic amine skeleton, such as4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB orα-NPD),N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: TPD),4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB), 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine(abbreviation: BPAFLP), 4-phenyl-3′-(9-phenylfluoren-9-yl)triphenylamine(abbreviation: mBPAFLP),4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation:PCBA1BP), 3-[4-(9-phenanthryl)-phenyl]-9-phenyl-9H-carbazole(abbreviation: PCPPn),N-(4-biphenyl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9-phenyl-9H-carbazol-3-amine(abbreviation: PCBiF),N-(1,1′-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF),4,4′-diphenyl-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBBi1BP),4-(1-naphthyl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBANB),4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBNBB),9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine(abbreviation: PCBAF),N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9′-bifluoren-2-amine(abbreviation: PCBASF), 4,4′,4″-tris(carbazol-9-yl)triphenylamine(abbreviation: TCTA), 4,4′,4″-tris(N,N′-diphenylamino)triphenylamine(abbreviation: TDATA), and4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbreviation: MTDATA); compounds having a carbazole skeleton, such as1,3-bis(N-carbazolyl)benzene (abbreviation: mCP),4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP),3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP),3,3′-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP),3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1),3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2),3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene(abbreviation: TCPB), and9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA);compounds having a thiophene skeleton, such as4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation:DBT3P-II),2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene(abbreviation: DBTFLP-III), and4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene(abbreviation: DBTFLP-IV); and compounds having a furan skeleton, suchas 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation:DBF3P-II) and4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran(abbreviation: mmDBFFLBi-II).

A high molecular compound such as poly(N-vinylcarbazole) (abbreviation:PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA),poly[N-(4-{N-[4-(4-diphenylamino)phenyl]phenyl-N-phenylamino}phenyl)methacrylamide](abbreviation:PTPDMA), or poly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine](abbreviation: Poly-TPD) can also be used.

Note that the hole-transport material is not limited to the aboveexamples and may be one of or a combination of various known materialswhen used for the hole-injection layers (1211, 1211 a, and 1211 b) andthe hole-transport layers (1212, 1212 a, and 1212 b). Note that thehole-transport layers (1212, 1212 a, and 1212 b) may each be formed of aplurality of layers. That is, for example, the hole-transport layers mayeach have a stacked-layer structure of a first hole-transport layer anda second hole-transport layer.

In the light-emitting element in FIG. 12D, the light-emitting layer 1213a is formed over the hole-transport layer 1212 a of the EL layer 1203 aby a vacuum evaporation method. After the EL layer 1203 a and the chargegeneration layer 1204 are formed, the light-emitting layer 1213 b isformed over the hole-transport layer 1212 b of the EL layer 1203 b by avacuum evaporation method.

<Light-Emitting Layer>

The light-emitting layers (1213, 1213 a, and 1213 b) each contain alight-emitting substance. Note that as the light-emitting substance, asubstance whose emission color is blue, violet, bluish violet, green,yellowish green, yellow, orange, red, or the like is appropriately used.When these light-emitting layers (1213 a and 1213 b) are formed usingdifferent light-emitting substances, different emission colors can beexhibited (for example, complementary emission colors are combined toachieve white light emission). Furthermore, a stacked-layer structure inwhich one light-emitting layer contains two or more kinds oflight-emitting substances may be employed.

The light-emitting layers (1213, 1213 a, and 1213 b) may each containone or more kinds of organic compounds (a host material and an assistmaterial) in addition to a light-emitting substance (guest material). Asthe one or more kinds of organic compounds, one or both of thehole-transport material and the electron-transport material described inthis embodiment can be used.

In the light-emitting element, it is preferable that a light-emittingsubstance which emits blue light (a blue-light-emitting substance) beused as a guest material in one of the light-emitting layers 1213 a and1213 b and a substance which emits green light (a green-light-emittingsubstance) and a substance which emits red light (a red-light-emittingsubstance) be used in the other light-emitting layer. This manner iseffective in the case where the blue-light-emitting substance (theblue-light-emitting layer) has lower light luminous efficiency or ashorter lifetime than the substances (layers) which emit other colors.Here, it is preferable that a light-emitting substance that convertssinglet excitation energy into light emission in the visible light rangebe used as the blue-light-emitting substance and light-emittingsubstances that convert triplet excitation energy into light emission inthe visible light range be used as the green- and red-light-emittingsubstances, whereby the spectrum balance between R, G, and B isimproved.

There is no particular limitation on the light-emitting substances thatcan be used for the light-emitting layers (1213, 1213 a, and 1213 b),and a light-emitting substance that converts singlet excitation energyinto light emission in the visible light range or a light-emittingsubstance that converts triplet excitation energy into light emission inthe visible light range can be used. Examples of the light-emittingsubstance are given below.

As an example of the light-emitting substance that converts singletexcitation energy into light emission, a substance that emitsfluorescence (fluorescent material) can be given. Examples of thesubstance that emits fluorescence include pyrene derivatives, anthracenederivatives, triphenylene derivatives, fluorene derivatives, carbazolederivatives, dibenzothiophene derivatives, dibenzofuran derivatives,dibenzoquinoxaline derivatives, quinoxaline derivatives, pyridinederivatives, pyrimidine derivatives, phenanthrene derivatives, andnaphthalene derivatives. Pyrene derivatives are particularly preferablebecause they have a high emission quantum yield. Specific examples ofpyrene derivatives includeN,N′-bis(3-methylphenyl)-N,N′-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine(abbreviation: 1,6mMemFLPAPm),N,N′-diphenyl-N,N′-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine(abbreviation: 1,6FLPAPm),N,N′-bis(dibenzofuran-2-yl)-N,N′-diphenylpyrene-1,6-diamine(abbreviation: 1,6FrAPm),N,N′-bis(dibenzothiophen-2-yl)-N,N′-diphenylpyrene-1,6-diamine(abbreviation: 1,6ThAPm),N,N′-(pyrene-1,6-diyl)bis[(N-phenylbenzo[b]naphtho[1,2-d]furan)-6-amine](abbreviation:1,6BnfAPm),N,N′-(pyrene-1,6-diyl)bis[(N-phenylbenzo[b]naphtho[1,2-d]furan)-8-amine](abbreviation: 1,6BnfAPm-02), andN,N′-(pyrene-1,6-diyl)bis[(6,N-diphenylbenzo[b]naphtho[1,2-d]furan)-8-amine](abbreviation: 1,6BnfAPm-03). In addition, pyrene derivatives arecompounds effective for meeting the chromaticity of blue in oneembodiment of the present invention.

In addition, it is possible to use5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2′-bipyridine (abbreviation:PAP2BPy), 5,6-bis[4′-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2′-bipyridine(abbreviation: PAPP2BPy),N,N′-bis[4-(9H-carbazol-9-yl)phenyl]-N,N′-diphenylstilbene-4,4′-diamine(abbreviation: YGA2S),4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-anthryl)triphenylamine(abbreviation: YGAPA),4-(9H-carbazol-9-yl)-4′-(9,10-diphenyl-2-anthryl)triphenylamine(abbreviation: 2YGAPPA),N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: PCAPA),4-(10-phenyl-9-anthryl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBAPA),4-[4-(10-phenyl-9-anthryl)phenyl]-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBAPBA), perylene, 2,5,8,11-tetra(tert-butyl)perylene(abbreviation: TBP),N,N′-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis[N,N′,N′-triphenyl-1,4-phenylenediamine](abbreviation: DPABPA),N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: 2PCAPPA),N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N′,N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPAPPA), or the like.

As examples of a light-emitting substance that converts tripletexcitation energy into light emission, a substance that emitsphosphorescence (phosphorescent material) and a thermally activateddelayed fluorescence (TADF) material that exhibits thermally activateddelayed fluorescence can be given.

Examples of a phosphorescent material include an organometallic complex,a metal complex (platinum complex), and a rare earth metal complex.These substances exhibit the respective emission colors (emission peaks)and thus, any of them is appropriately selected according to need.

As examples of a phosphorescent material which emits blue or green lightand whose emission spectrum has a peak wavelength at greater than orequal to 450 nm and less than or equal to 570 nm, the followingsubstances can be given.

For example, organometallic complexes having a 4H-triazole skeleton,such as tris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN²]phenyl-κC}iridium(III)(abbreviation: [Ir(mpptz-dmp)₃]),tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III)(abbreviation: [Ir(Mptz)₃]),tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(iPrptz-3b)₃]), andtris[3-(5-biphenyl)-5-isopropyl-4-phenyl-4H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(iPr5btz)₃]); organometallic complexes having a1H-triazole skeleton, such astris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(Mptzl-mp)₃]) andtris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III)(abbreviation: [Ir(Prptzl-Me)₃]); organometallic complexes having animidazole skeleton, such asfac-tris[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III)(abbreviation: [Ir(iPrpmi)₃]) andtris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III)(abbreviation: [Ir(dmpimpt-Me)₃]); organometallic complexes in which aphenylpyridine derivative having an electron-withdrawing group is aligand, such asbis[2-(4′,6′-difluorophenyl)pyridinato-N,C²′]iridium(III)tetrakis(1-pyrazolyl)borate (abbreviation: FIr6),bis[2-(4′,6′-difluorophenyl)pyridinato-N,C²′]iridium(III) picolinate(abbreviation: FIrpic),bis[2-(3,5-bistrifluoromethyl-phenyl)-pyridinato-N,C²′]iridium(III)picolinate (abbreviation: [Ir(CF₃ppy)₂(pic)]), andbis[2-(4′,6′-difluorophenyl)pyridinato-N,C²′]iridium(III)acetylacetonate (abbreviation: FIr(acac)); and the like can be given.

As examples of a phosphorescent material which emits green or yellowlight and whose emission spectrum has a peak wavelength at greater thanor equal to 495 nm and less than or equal to 590 nm, the followingsubstances can be given.

For example, organometallic iridium complexes having a pyrimidineskeleton, such as tris(4-methyl-6-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(mppm)₃]),tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation:[Ir(tBuppm)₃]),(acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(mppm)₂(acac)]),(acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(tBuppm)₂(acac)]),(acetylacetonato)bis[6-(2-norbomyl)-4-phenylpyrimidinato]iridium(III)(abbreviation: [Ir(nbppm)₂(acac)]),(acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III)(abbreviation: [Ir(mpmppm)₂(acac)]), (acetylacetonato)bis{4,6-dimethyl-2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κN³]phenyl-κC}iridium(III)(abbreviation: [Ir(dmppm-dmp)₂(acac)]), and(acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III)(abbreviation: [Ir(dppm)₂(acac)]); organometallic iridium complexeshaving a pyrazine skeleton, such as(acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III)(abbreviation: [Ir(mppr-Me)₂(acac)]) and(acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III)(abbreviation: [Ir(mppr-iPr)₂(acac)]); organometallic iridium complexeshaving a pyridine skeleton, such astris(2-phenylpyridinato-N,C²′)iridium(III) (abbreviation: [Ir(ppy)₃]),bis(2-phenylpyridinato-N,C²′)iridium(III) acetylacetonate (abbreviation:[Ir(ppy)₂(acac)]), bis(benzo[h]quinolinato)iridium(III) acetylacetonate(abbreviation: [Ir(bzq)₂(acac)]), tris(benzo[h]quinolinato)iridium(III)(abbreviation: [Ir(bzq)₃]), tris(2-phenylquinolinato-N,C²′)iridium(III)(abbreviation: [Ir(pq)₃]), andbis(2-phenylquinolinato-N,C²′)iridium(III) acetylacetonate(abbreviation: [Ir(pq)₂(acac)]); organometallic complexes such asbis(2,4-diphenyl-1,3-oxazolato-N,C²′)iridium(III) acetylacetonate(abbreviation: [Ir(dpo)₂(acac)]),bis{2-[4′-(perfluorophenyl)phenyl]pyridinato-N,C²′}iridium(III)acetylacetonate (abbreviation: [Ir(p-PF-ph)₂(acac)]), andbis(2-phenylbenzothiazolato-N,C²′)iridium(III) acetylacetonate(abbreviation: [Ir(bt)₂(acac)]); and rare earth metal complexes such astris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation:[Tb(acac)₃(Phen)]) can be given.

Among the above, organometallic iridium complexes having a pyridineskeleton (particularly, a phenylpyridine skeleton) or a pyrimidineskeleton are compounds effective for meeting the chromaticity of greenin one embodiment of the present invention.

As examples of a phosphorescent material which emits yellow or red lightand whose emission spectrum has a peak wavelength at greater than orequal to 570 nm and less than or equal to 750 nm, the followingsubstances can be given.

For example, organometallic complexes having a pyrimidine skeleton, suchas(diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III)(abbreviation: [Ir(5mdppm)₂(dibm)]),bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III)(abbreviation: [Ir(5mdppm)₂(dpm)]), and(dipivaloylmethanato)bis[4,6-di(naphthalen-1-yl)pyrimidinato]iridium(III)(abbreviation: [Ir(dlnpm)₂(dpm)]); organometallic complexes having apyrazine skeleton, such as(acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III)(abbreviation: [Ir(tppr)₂(acac)]),bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III)(abbreviation: [Ir(tppr)₂(dpm)]), bis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-κNV]phenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-P)₂(dibm)]),bis{4,6-dimethyl-2-[5-(4-cyano-2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,2,6,6-tetramethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-dmCP)₂(dpm)]),(acetylacetonato)bis[2-methyl-3-phenylquinoxalinato-N,C²′]iridium(III)(abbreviation: [Ir(mpq)₂(acac)]),(acetylacetonato)bis(2,3-diphenylquinoxalinato-N,C²′)iridium(III)(abbreviation: [Ir(dpq)₂(acac)]), and(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)(abbreviation: [Ir(Fdpq)₂(acac)]); organometallic complexes having apyridine skeleton, such astris(1-phenylisoquinolinato-N,C²′)iridium(III) (abbreviation:[Ir(piq)₃]) and bis(1-phenylisoquinolinato-N,C²′)iridium(III)acetylacetonate (abbreviation: [Ir(piq)₂(acac)]); platinum complexessuch as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrinplatinum(II)(abbreviation: [PtOEP]); and rare earth metal complexes such astris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III)(abbreviation: [Eu(DBM)₃(Phen)]) andtris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III)(abbreviation: [Eu(TTA)₃(Phen)]) can be given.

Among the above, organometallic iridium complexes having a pyrazineskeleton are compounds effective for meeting the chromaticity of red inone embodiment of the present invention. In particular, organometalliciridium complexes having a cyano group (e.g., [Ir(dmdppr-dmCP)₂(dpm)])are preferable because they are stable.

Note that as the blue-light-emitting substance, a substance whosephotoluminescence peak wavelength is greater than or equal to 430 nm andless than or equal to 470 nm, preferably greater than or equal to 430 nmand less than or equal to 460 nm may be used. As thegreen-light-emitting substance, a substance whose photoluminescence peakwavelength is greater than or equal to 500 nm and less than or equal to540 nm, preferably greater than or equal to 500 nm and less than orequal to 530 nm may be used. As the red-light-emitting substance, asubstance whose photoluminescence peak wavelength is greater than orequal to 610 nm and less than or equal to 680 nm, preferably greaterthan or equal to 620 nm and less than or equal to 680 nm may be used.Note that the photoluminescence may be measured with either a solutionor a thin film.

With the parallel use of such compounds and microcavity effect, theabove chromaticity can be more easily met. Here, a transflectiveelectrode (a metal thin film portion) that is needed for obtainingmicrocavity effect preferably has a thickness of greater than or equalto 20 nm and less than or equal to 40 nm, and further preferably greaterthan 25 nm and less than or equal to 40 nm. However, the thicknessgreater than 40 nm possibly reduces the efficiency.

As the organic compounds (the host material and the assist material)used in the light-emitting layers (1213, 1213 a, and 1213 b), one ormore kinds of substances having a larger energy gap than thelight-emitting substance (the guest material) are used. Note that thehole-transport materials listed above and the electron-transportmaterials given below can be used as the host material and the assistmaterial, respectively.

When the light-emitting substance is a fluorescent material, it ispreferable to use, as the host material, an organic compound that has ahigh energy level in a singlet excited state and has a low energy levelin a triplet excited state. For example, an anthracene derivative or atetracene derivative is preferably used. Specific examples include9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation:PCzPA), 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation:PCPN), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation:CzPA), 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole(abbreviation: cgDBCzPA),6-[3-(9,10-diphenyl-2-anthryl)phenyl]-benzo[b]naphtho[1,2-d]furan(abbreviation: 2mBnfPPA),9-phenyl-10-{4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4′-yl}anthracene(abbreviation: FLPPA), 5,12-diphenyltetracene, and5,12-bis(biphenyl-2-yl)tetracene.

In the case where the light-emitting substance is a phosphorescentmaterial, an organic compound having triplet excitation energy (energydifference between a ground state and a triplet excited state) which ishigher than that of the light-emitting substance can be selected as thehost material. In that case, it is possible to use a zinc- oraluminum-based metal complex, an oxadiazole derivative, a triazolederivative, a benzimidazole derivative, a quinoxaline derivative, adibenzoquinoxaline derivative, a dibenzothiophene derivative, adibenzofuran derivative, a pyrimidine derivative, a triazine derivative,a pyridine derivative, a bipyridine derivative, a phenanthrolinederivative, an aromatic amine, a carbazole derivative, and the like.

Specific examples include metal complexes such astris(8-quinolinolato)aluminum(III) (abbreviation: Alq),tris(4-methyl-8-quinolinolato)aluminum(III) (abbreviation: Almq₃),bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq₂),bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III)(abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq),bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), andbis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ);heterocyclic compounds such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole(abbreviation: TAZ),2,2′,2″-(1,3,5-benzenetriyl)-tris(1-phenyl-1H-benzimidazole)(abbreviation: TPBI), bathophenanthroline (abbreviation: BPhen),bathocuproine (abbreviation: BCP),2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation:NBphen), and 9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole(abbreviation: CO11); and aromatic amine compounds such as NPB, TPD, andBSPB.

In addition, condensed polycyclic aromatic compounds such as anthracenederivatives, phenanthrene derivatives, pyrene derivatives, chrysenederivatives, and dibenzo[g,p]chrysene derivatives can be used.Specifically, 9,10-diphenylanthracene (abbreviation: DPAnth),N,N-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: CzA1PA), 4-(10-phenyl-9-anthryl)triphenylamine(abbreviation: DPhPA), YGAPA, PCAPA,N,9-diphenyl-N-{4-[4-(10-phenyl-9-anthryl)phenyl]phenyl}-9H-carbazol-3-amine(abbreviation: PCAPBA),9,10-diphenyl-2-[N-phenyl-N-(9-phenyl-9H-carbazol-3-yl)amino]anthracene(abbreviation: 2PCAPA), 6,12-dimethoxy-5,11-diphenylchrysene,N,N,N′,N′,N″,N″,N′″,N′″-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine(abbreviation: DBC1), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole(abbreviation: CzPA),3,6-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole(abbreviation: DPCzPA), 9,10-bis(3,5-diphenylphenyl)anthracene(abbreviation: DPPA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA),2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA),9,9′-bianthryl (abbreviation: BANT),9,9′-(stilbene-3,3′-diyl)diphenanthrene (abbreviation: DPNS),9,9′-(stilbene-4,4′-diyl)diphenanthrene (abbreviation: DPNS2),1,3,5-tri(1-pyrenyl)benzene (abbreviation: TPB3), or the like can beused.

In the case where a plurality of organic compounds are used for thelight-emitting layers (1213, 1213 a, and 1213 b), it is preferable touse compounds that form an exciplex in combination with a light-emittingsubstance. In that case, although any of various organic compounds canbe combined appropriately to be used, to form an exciplex efficiently,it is particularly preferable to combine a compound that easily acceptsholes (hole-transport material) and a compound that easily acceptselectrons (electron-transport material). As the hole-transport materialand the electron-transport material, specifically, any of the materialsdescribed in this embodiment can be used.

The TADF material is a material that can up-convert a triplet excitedstate into a singlet excited state (i.e., reverse intersystem crossingis possible) using a little thermal energy and efficiently exhibitslight emission (fluorescence) from the singlet excited state. The TADFis efficiently obtained under the condition where the difference inenergy between the triplet excited level and the singlet excited levelis greater than or equal to 0 eV and less than or equal to 0.2 eV,preferably greater than or equal to 0 eV and less than or equal to 0.1eV. Note that “delayed fluorescence” exhibited by the TADF materialrefers to light emission having the same spectrum as normal fluorescenceand an extremely long lifetime. The lifetime is 10⁻⁶ seconds or longer,preferably 10⁻³ seconds or longer.

Examples of the TADF material include fullerene, a derivative thereof,an acridine derivative such as proflavine, and eosin. Other examplesinclude a metal-containing porphyrin, such as a porphyrin containingmagnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium(In), or palladium (Pd). Examples of the metal-containing porphyrininclude a protoporphyrin-tin fluoride complex (SnF₂(Proto IX)), amesoporphyrin-tin fluoride complex (SnF₂(Meso IX)), ahematoporphyrin-tin fluoride complex (SnF₂(Hemato IX)), a coproporphyrintetramethyl ester-tin fluoride complex (SnF₂(Copro III-4Me)), anoctaethylporphyrin-tin fluoride complex (SnF₂(OEP)), anetioporphyrin-tin fluoride complex (SnF₂(Etio I)), and anoctaethylporphyrin-platinum chloride complex (PtCl₂OEP).

Alternatively, a heterocyclic compound having a π-electron richheteroaromatic ring and a π-electron deficient heteroaromatic ring, suchas2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine(PIC-TRZ),2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine(PCCzPTzn),2-[4-(10H-phenoxazin-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine(PXZ-TRZ),3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole(PPZ-3TPT), 3-(9,9-dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one (ACRXTN),bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (DMAC-DPS), or10-phenyl-10H,10′H-spiro[acridin-9,9′-anthracen]-10′-one (ACRSA) can beused. Note that a substance in which the π-electron rich heteroaromaticring is directly bonded to the π-electron deficient heteroaromatic ringis particularly preferable because both the donor property of thet-electron rich heteroaromatic ring and the acceptor property of theπ-electron deficient heteroaromatic ring are increased and the energydifference between the singlet excited state and the triplet excitedstate becomes small.

Note that when a TADF material is used, the TADF material can becombined with another organic compound.

In the light-emitting element in FIG. 12D, the electron-transport layer1214 a is formed over the light-emitting layer 1213 a of the EL layer1203 a by a vacuum evaporation method. After the EL layer 1203 a and thecharge generation layer 1204 are formed, the electron-transport layer1214 b is formed over the light-emitting layer 1213 b of the EL layer1203 b by a vacuum evaporation method.

<Electron-Transport Layer>

The electron-transport layers (1214, 1214 a, and 1214 b) transport theelectrons, which are injected from the second electrode 1202 by theelectron-injection layers (1215, 1215 a, and 1215 b), to thelight-emitting layers (1213, 1213 a, and 1213 b). Note that theelectron-transport layers (1214, 1214 a, and 1214 b) each contain anelectron-transport material. It is preferable that theelectron-transport materials included in the electron-transport layers(1214, 1214 a, and 1214 b) be substances with an electron mobility ofhigher than or equal to 1×10⁻⁶ cm²/Vs. Note that other substances mayalso be used as long as the substances have an electron-transportproperty higher than a hole-transport property.

Examples of the electron-transport material include metal complexeshaving a quinoline ligand, a benzoquinoline ligand, an oxazole ligand,and a thiazole ligand; an oxadiazole derivative; a triazole derivative;a phenanthroline derivative; a pyridine derivative; and a bipyridinederivative. In addition, a π-electron deficient heteroaromatic compoundsuch as a nitrogen-containing heteroaromatic compound can also be used.

Specifically, it is possible to use metal complexes such as Alq₃,tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq₃),bis(10-hydroxybenzo[h]quinolinato)beryllium (abbreviation: BeBq₂), BAlq,Zn(BOX)₂, and bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (abbreviation:Zn(BTZ)₂), heteroaromatic compounds such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),3-(4′-tert-butylphenyl)-4-phenyl-5-(4″-biphenyl)-1,2,4-triazole(abbreviation: TAZ),3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: Bphen),bathocuproine (abbreviation: BCP), and4,4′-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs), andquinoxaline derivatives and dibenzoquinoxaline derivatives such as2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:2mDBTPDBq-II),2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mDBTBPDBq-II),2-[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[fh]quinoxaline(abbreviation: 2CzPDBq-III),7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:7mDBTPDBq-II), and6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:6mDBTPDBq-II).

Alternatively, a high molecular compound such as poly(2,5-pyridinediyl)(abbreviation: PPy),poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)](abbreviation: PF-Py), orpoly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2′-bipyridine-6,6′-diyl)](abbreviation: PF-BPy) can be used.

Each of the electron-transport layers (1214, 1214 a, and 1214 b) is notlimited to a single layer, but may be a stack of two or more layers eachcontaining any of the above substances.

In the light-emitting element in FIG. 12D, the electron-injection layer1215 a is formed over the electron-transport layer 1214 a of the ELlayer 1203 a by a vacuum evaporation method. Subsequently, the EL layer1203 a and the charge generation layer 1204 are formed, the componentsup to the electron-transport layer 1214 b of the EL layer 1203 b areformed and then, the electron-injection layer 1215 b is formed thereoverby a vacuum evaporation method.

<Electron-Injection Layer>

The electron-injection layers (1215, 1215 a, and 1215 b) each contain asubstance having a high electron-injection property. Theelectron-injection layers (1215, 1215 a, and 1215 b) can each be formedusing an alkali metal, an alkaline earth metal, or a compound thereof,such as lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride(CaF₂), or lithium oxide (LiO_(x)). A rare earth metal compound likeerbium fluoride (ErF₃) can also be used. Electride may also be used forthe electron-injection layers (1215, 1215 a, and 1215 b). Examples ofthe electride include a substance in which electrons are added at highconcentration to calcium oxide-aluminum oxide. Any of the substances forforming the electron-transport layers (1214, 1214 a, and 1214 b), whichare given above, can also be used.

A composite material in which an organic compound and an electron donor(donor) are mixed may also be used for the electron-injection layers(1215, 1215 a, and 1215 b). Such a composite material is excellent in anelectron-injection property and an electron-transport property becauseelectrons are generated in the organic compound by the electron donor.The organic compound here is preferably a material excellent intransporting the generated electrons; specifically, for example, theelectron-transport materials for forming the electron-transport layers(1214, 1214 a, and 1214 b) (e.g., a metal complex or a heteroaromaticcompound) can be used. As the electron donor, a substance showing anelectron-donating property with respect to the organic compound may beused. Preferable examples are an alkali metal, an alkaline earth metal,and a rare earth metal. Specifically, lithium, cesium, magnesium,calcium, erbium, ytterbium, and the like can be given. Furthermore, analkali metal oxide and an alkaline earth metal oxide are preferable, andlithium oxide, calcium oxide, barium oxide, and the like can be given.Alternatively, a Lewis base such as magnesium oxide can be used. Furtheralternatively, an organic compound such as tetrathiafulvalene(abbreviation: TTF) can be used.

In the case where light obtained from the light-emitting layer 1213 b isamplified in the light-emitting element illustrated in FIG. 12D, forexample, the optical path length between the second electrode 1202 andthe light-emitting layer 1213 b is preferably less than one fourth ofthe wavelength λ of light emitted from the light-emitting layer 1213 b.In that case, the optical path length can be adjusted by changing thethickness of the electron-transport layer 1214 b or theelectron-injection layer 1215 b.

<Charge Generation Layer>

In the light-emitting element illustrated in FIG. 12D, the chargegeneration layer 1204 has a function of injecting electrons into the ELlayer 1203 a and injecting holes into the EL layer 1203 b when a voltageis applied between the first electrode (anode) 1201 and the secondelectrode (cathode) 1202. The charge generation layer 1204 may haveeither a structure in which an electron acceptor (acceptor) is added toa hole-transport material or a structure in which an electron donor(donor) is added to an electron-transport material. Alternatively, bothof these structures may be stacked. Note that forming the chargegeneration layer 1204 by using any of the above materials can suppressan increase in drive voltage caused by the stack of the EL layers.

In the case where the charge generation layer 1204 has a structure inwhich an electron acceptor is added to a hole-transport material, any ofthe materials described in this embodiment can be used as thehole-transport material. As the electron acceptor, it is possible to use7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:F4-TCNQ), chloranil, and the like. In addition, an oxide of metals thatbelong to Group 4 to Group 8 of the periodic table can be given.Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromiumoxide, molybdenum oxide, tungsten oxide, manganese oxide, rhenium oxide,or the like can be used.

In the case where the charge generation layer 1204 has a structure inwhich an electron donor is added to an electron-transport material, anyof the materials described in this embodiment can be used as theelectron-transport material. As the electron donor, it is possible touse an alkali metal, an alkaline earth metal, a rare earth metal, metalsthat belong to Groups 2 and 13 of the periodic table, or an oxide orcarbonate thereof. Specifically, lithium (Li), cesium (Cs), magnesium(Mg), calcium (Ca), ytterbium (Yb), indium (In), lithium oxide, cesiumcarbonate, or the like is preferably used. Alternatively, an organiccompound such as tetrathianaphthacene may be used as the electron donor.

For fabrication of the light-emitting element in this embodiment, avacuum process such as an evaporation method or a solution process suchas a spin coating method or an ink-jet method can be used. When anevaporation method is used, a physical vapor deposition method (PVDmethod) such as a sputtering method, an ion plating method, an ion beamevaporation method, a molecular beam evaporation method, or a vacuumevaporation method, a chemical vapor deposition method (CVD method), orthe like can be used. Specifically, the functional layers (thehole-injection layers, the hole-transport layers, the light-emittinglayers, the electron-transport layers, the electron-injection layers)included in the EL layers and the charge generation layer of thelight-emitting element can be formed by an evaporation method (e.g., avacuum evaporation method), a coating method (e.g., a dip coatingmethod, a die coating method, a bar coating method, a spin coatingmethod, or a spray coating method), a printing method (e.g., an ink-jetmethod, screen printing (stencil), offset printing (planography),flexography (relief printing), gravure printing, or micro-contactprinting), or the like.

Note that materials that can be used for the functional layers (thehole-injection layers, the hole-transport layers, the light-emittinglayers, the electron-transport layers, and the electron-injectionlayers) that are included in the EL layers and the charge generationlayer in the light-emitting element described in this embodiment are notlimited to the above materials, and other materials can be used incombination as long as the functions of the layers are fulfilled. Forexample, a high molecular compound (e.g., an oligomer, a dendrimer, or apolymer), a middle molecular compound (a compound between a lowmolecular compound and a high molecular compound with a molecular weightof 400 to 4000), an inorganic compound (e.g., a quantum dot material),or the like can be used. The quantum dot may be a colloidal quantum dot,an alloyed quantum dot, a core-shell quantum dot, a core quantum dot, orthe like.

Structure Example of Light-Emitting Panel

FIG. 13A illustrates a light-emitting panel of one embodiment of thepresent invention. The light-emitting panel illustrated in FIG. 13A isan active matrix light-emitting panel in which transistors (FETs) 1302are electrically connected to light-emitting elements (1303R, 1303G,1303B, and 1303W) over a first substrate 1301. These light-emittingelements (1303R, 1303G, 1303B, and 1303W) share an EL layer 1304 andeach have a microcavity structure in which the optical path lengthbetween electrodes is adjusted depending on the emission color of thelight-emitting element. The light-emitting panel is a top-emissionlight-emitting panel in which light is emitted from the EL layer 1304through color filters (1306R, 1306G, and 1306B) formed on a secondsubstrate 1305.

The light-emitting panel illustrated in FIG. 13A is fabricated such thata first electrode 1307 functions as a reflective electrode and a secondelectrode 1308 functions as a transflective electrode.

In the case where the light-emitting element 1303R functions as a redlight-emitting element, the light-emitting element 1303G functions as agreen light-emitting element, the light-emitting element 1303B functionsas a blue light-emitting element, and the light-emitting element 1303Wfunctions as a white light-emitting element in FIG. 13A, for example, agap between the first electrode 1307 and the second electrode 1308 inthe light-emitting element 1303R is adjusted to have an optical pathlength 1316R, a gap between the first electrode 1307 and the secondelectrode 1308 in the light-emitting element 1303G is adjusted to havean optical path length 1316G, and a gap between the first electrode 1307and the second electrode 1308 in the light-emitting element 1303B isadjusted to have an optical path length 1316B as illustrated in FIG.13B. Note that optical adjustment can be performed in such a manner thata conductive layer 1310R is stacked over the first electrode 1307 in thelight-emitting element 1303R and a conductive layer 1310G is stackedover the first electrode 1307 in the light-emitting element 1303G asillustrated in FIG. 13B.

The second substrate 1305 is provided with the color filters (1306R,1306G, and 1306B). Note that the color filters each transmit visiblelight in a specific wavelength range and blocks visible light in aspecific wavelength range. Thus, as illustrated in FIG. 13A, the colorfilter 1306R that transmits only light in the red wavelength range isprovided in a position overlapping with the light-emitting element1303R, whereby red light emission can be obtained from thelight-emitting element 1303R. Furthermore, the color filter 1306G thattransmits only light in the green wavelength range is provided in aposition overlapping with the light-emitting element 1303G, wherebygreen light emission can be obtained from the light-emitting element1303G. Moreover, the color filter 1306B that transmits only light in theblue wavelength range is provided in a position overlapping with thelight-emitting element 1303B, whereby blue light emission can beobtained from the light-emitting element 1303B. Note that thelight-emitting element 1303W can emit white light without a colorfilter. Note that a black layer (black matrix) 1309 may be provided atan end portion of each color filter. The color filters (1306R, 1306G,and 1306B) and the black layer 1309 may be covered with an overcoatlayer formed using a material transmitting visible light.

Although the light-emitting panel in FIG. 13A has a structure in whichlight is extracted from the second substrate 1305 side (top-emissionstructure), a structure in which light is extracted from the firstsubstrate 1301 side where the FETs 1302 are formed (bottom-emissionstructure) may be employed. Note that in the light-emitting panel havinga top-emission structure, the first substrate 1301 can be alight-blocking substrate or a light-transmitting substrate, whereas in alight-emitting panel having a bottom-emission structure, the firstsubstrate 1301 needs to be a light-transmitting substrate.

In FIG. 13A, the light-emitting elements are the red light-emittingelement, the green light-emitting element, the blue light-emittingelement, and the white light-emitting element; however, thelight-emitting elements of one embodiment of the present invention arenot limited to the above, and a yellow light-emitting element or anorange light-emitting element may be used. Note that description in anyof the other embodiments can be referred to as appropriate for materialsthat are used for the EL layers (a light-emitting layer, ahole-injection layer, a hole-transport layer, an electron-transportlayer, an electron-injection layer, a charge generation layer, and thelike) to fabricate each of the light-emitting elements. In that case, acolor filter needs to be appropriately selected depending on theemission color of the light-emitting element.

With the above structure, a light-emitting panel includinglight-emitting elements that exhibit a plurality of emission colors canbe fabricated.

This embodiment can be combined with any of other embodiments asappropriate.

Embodiment 3

In this embodiment, a display panel that can be used for the displaydevice of one embodiment of the present invention is described withreference to the drawings.

In this embodiment, a display panel that uses an EL element as a displayelement is described as an example. The display panel in this embodimentcan display an image with a wide color gamut by being combined with thestructure described in Embodiment 1 or the like.

The display panel can have a structure in which sub-pixels of threecolors of red (R), green (G), and blue (B) express one color, astructure in which sub-pixels of four colors of R, G, B, and white (W)express one color, a structure in which sub-pixels of four colors of R,G, B, and yellow (Y) express one color, or the like. There is noparticular limitation on the color element and colors other than R, G,B, W, and Y (e.g., cyan or magenta) may be used.

Example of Top View of Display Panel

FIGS. 14A and 14B show top views of a display panel 370.

The display panels 370 illustrated in FIGS. 14A and 14B each include theregion 110 transmitting visible light, a display portion 381, and adriver circuit portion 382. In the example illustrated in FIG. 14A, theregion 110 transmitting visible light is adjacent to the display portion381 and provided along two sides of the display portion 381. In theexample illustrated in FIG. 14B, the region 110 transmitting visiblelight is adjacent to the display portion 381 and provided along threesides of the display portion 381.

Example 1 of Cross-Sectional Structure of Display Panel

FIG. 14C is a cross-sectional view of a display panel 370A employing aseparate coloring method and having a top-emission structure. FIG. 14Ccorresponds to cross-sectional views along dashed-dotted lines A1-A2 andA3-A4 in each of FIGS. 14A and 14B.

The display panel 370A includes the substrate 201, the bonding layer203, the insulating layer 205, a plurality of transistors, a capacitor305, a conductive layer 307, an insulating layer 312, an insulatinglayer 313, an insulating layer 314, an insulating layer 315, alight-emitting element 304, a conductive layer 355, a spacer 316, abonding layer 317, the substrate 211, the bonding layer 213, and theinsulating layer 215.

The layers included in the region 110 transmitting visible lighttransmit visible light. FIG. 14C illustrates an example where the region110 transmitting visible light includes the substrate 201, the bondinglayer 203, the insulating layer 205, a gate insulating layer 311, theinsulating layer 312, the insulating layer 313, the insulating layer314, the bonding layer 317, the insulating layer 215, the bonding layer213, and the substrate 211. In this stacked-layer structure, thematerials for the layers are preferably selected such that a differencein refractive index at each interface is minimized.

The driver circuit portion 382 includes a transistor 301. The displayportion 381 includes a transistor 302 and a transistor 303.

Each transistor includes a gate, the gate insulating layer 311, asemiconductor layer, a back gate, a source, and a drain. The gate (thelower gate) and the semiconductor layer overlap with each other with thegate insulating layer 311 provided therebetween. Part of the gateinsulating layer 311 functions as a dielectric of the capacitor 305. Theconductive layer functioning as the source or the drain of thetransistor 302 serves as one electrode of the capacitor 305. The backgate (the upper gate) and the semiconductor layer overlap with eachother with the insulating layer 312 and the insulating layer 313provided therebetween.

The structure of the transistor may be different between the drivercircuit portion 382 and the display portion 381. The driver circuitportion 382 and the display portion 381 may each include a plurality ofkinds of transistors.

The transistors 301, 302, and 303 illustrated in FIG. 14C each includetwo gates, the gate insulating layer 311, a semiconductor layer, asource, and a drain. FIG. 14C illustrates an example where eachtransistor has a structure in which the semiconductor layer issandwiched between the two gates. Such transistors can have higherfield-effect mobility and thus have higher on-state current than othertransistors. Consequently, a circuit capable of high-speed operation canbe obtained. Furthermore, the area occupied by a circuit can be reduced.The use of the transistor having high on-state current can reduce signaldelay in wirings and can reduce display luminance variation even in adisplay panel in which the number of wirings is increased because ofincrease in size or resolution.

The capacitor 305 includes a pair of electrodes and the dielectrictherebetween. The capacitor 305 includes a conductive layer that isformed using the same material and the same step as the gate (the lowergate) of the transistor and a conductive layer that is formed using thesame material and the same step as the source and the drain of thetransistor.

A material through which impurities such as water and hydrogen do noteasily diffuse is preferably used for at least one of the insulatinglayers 312, 313, and 314. Diffusion of impurities from the outside intothe transistors can be effectively inhibited, leading to improvedreliability of the display panel. The insulating layer 314 functions asa planarization layer. In the example illustrated in FIG. 14C, theinsulating layer 314 is formed using an organic material and extendsover the entire area of the display panel. Such a structure ispreferable because the yield of the peeling process can be increased.Alternatively, a structure can be employed in which the insulating layerformed using an organic material is not placed in an end portion of thedisplay panel. This structure can inhibit entry of impurities into thelight-emitting element 304.

The insulating layer 205 and the substrate 201 are attached to eachother with the bonding layer 203. The insulating layer 215 and thesubstrate 211 are attached to each other with the bonding layer 213.

In the display portion 381, the light-emitting element 304 is positionedbetween the insulating layer 205 and the insulating layer 215. Entry ofimpurities into the light-emitting element 304 from the thicknessdirection of the display panel 370 is suppressed. Similarly, a pluralityof insulating layers covering the transistors are provided in thedisplay portion 381, and thus entry of impurities into the transistorsis suppressed.

The light-emitting element 304, the transistors, and the like arepreferably provided between a pair of insulating films that are highlyresistant to moisture, in which case entry of impurities such as waterinto these elements can be suppressed, leading to higher reliability ofthe display panel.

Examples of the insulating film highly resistant to moisture include afilm containing nitrogen and silicon (e.g., a silicon nitride film and asilicon nitride oxide film) and a film containing nitrogen and aluminum(e.g., an aluminum nitride film). Alternatively, a silicon oxide film, asilicon oxynitride film, an aluminum oxide film, or the like may beused.

For example, the moisture vapor transmission rate of the insulating filmhighly resistant to moisture is lower than or equal to 1×10⁻⁵[g/(m²·day)], preferably lower than or equal to 1×10⁻⁶ [g/(m²·day)],further preferably lower than or equal to 1×10⁷ [g/(m²·day)], stillfurther preferably lower than or equal to 1×10⁻⁸[g/(m²·day)].

The light-emitting element 304 includes an electrode 321, an EL layer322, and an electrode 323. The light-emitting element 304 may include anoptical adjustment layer 324. The light-emitting element 304 emits lightto the substrate 211 side.

The transistor, the capacitor, the wiring, and the like are provided tooverlap with a light-emitting region of the light-emitting element 304,whereby an aperture ratio of the display portion 381 can be increased.

One of the electrode 321 and the electrode 323 functions as an anode andthe other functions as a cathode. When a voltage higher than thethreshold voltage of the light-emitting element 304 is applied betweenthe electrode 321 and the electrode 323, holes are injected to the ELlayer 322 from the anode side and electrons are injected to the EL layer322 from the cathode side. The injected electrons and holes arerecombined in the EL layer 322 and a light-emitting substance containedin the EL layer 322 emits light.

The electrode 321 is electrically connected to the source or the drainof the transistor 303, directly or through another conductive layer. Theelectrode 321 functions as a pixel electrode and is provided for eachlight-emitting element 304. Two adjacent electrodes 321 are electricallyinsulated from each other by the insulating layer 315.

The EL layer 322 is a layer containing a light-emitting material. As thelight-emitting element 304, an organic EL element including an organiccompound as a light-emitting material can be favorably used.

The EL layer 322 includes at least one light-emitting layer.

The electrode 323 functions as a common electrode and is provided for aplurality of light-emitting elements 304. A fixed potential is suppliedto the electrode 323.

Note that one embodiment of the present invention is not limited to aseparate coloring method, and a color filter method, a color conversionmethod, a quantum dot method, or the like may be employed.

For details of the light-emitting element, Embodiments 1 and 2 can alsobe referred to.

The connection portion 306 includes the conductive layer 307 and theconductive layer 355. The conductive layer 307 and the conductive layer355 are electrically connected to each other. The conductive layer 307can be formed using the same material and the same step as those of thesource and the drain of the transistor. The conductive layer 355 iselectrically connected to an external input terminal through which asignal or a potential from the outside is transmitted to the drivercircuit portion 382. Here, an example in which an FPC 373 is provided asan external input terminal is shown. The FPC 373 and the conductivelayer 355 are electrically connected to each other through a connector319.

As the connector 319, any of various anisotropic conductive films (ACF),anisotropic conductive pastes (ACP), and the like can be used.

A flexible substrate is preferably used as each of the substrates 201and 211. For example, glass, quartz, a resin, a metal, an alloy, or asemiconductor that is thin enough to have flexibility can be used. Thesubstrate through which light is extracted from the light-emittingelement is formed using a material that transmits the light. Forexample, the thickness of the substrate is preferably greater than orequal to 1 μm and less than or equal to 200 μm, further preferablygreater than or equal to 1 μm and less than or equal to 100 μm, stillfurther preferably greater than or equal to 10 μm and less than or equalto 50 μm, and particularly preferably greater than or equal to 10 μm andless than or equal to 25 μm. The thickness and hardness of the flexiblesubstrate are set in the range where mechanical strength and flexibilitycan be balanced against each other. The flexible substrate may have asingle-layer structure or a stacked-layer structure.

A resin, which has a specific gravity smaller than that of glass, ispreferably used for the flexible substrate, in which case the displaypanel can be lightweight as compared with the case where glass is used.

The substrate is preferably formed using a material with high toughness.In that case, a display panel with high impact resistance that is lesslikely to be broken can be provided. For example, when a resin substrateor a thin metal or alloy substrate is used, the display panel can belightweight and robust as compared with the case where a glass substrateis used.

A metal material and an alloy material, which have high thermalconductivity, are preferable because they can easily conduct heat to thewhole substrate and accordingly can suppress a local temperature rise inthe display panel. The thickness of a substrate using a metal materialor an alloy material is preferably greater than or equal to 10 μm andless than or equal to 200 μm, further preferably greater than or equalto 20 μm and less than or equal to 50 m.

There is no particular limitation on a material of the metal substrateor the alloy substrate, but it is preferable to use, for example,aluminum, copper, nickel, or a metal alloy such as an aluminum alloy orstainless steel. Examples of a material for a semiconductor substrateinclude silicon.

Furthermore, when a material with high thermal emissivity is used forthe substrate, increase of the surface temperature of the display panelcan be suppressed, and breakage or a decrease in reliability of thedisplay panel can be suppressed. For example, the substrate may have astacked-layer structure of a metal substrate and a layer with highthermal emissivity (the layer can be formed using a metal oxide or aceramic material, for example).

Examples of materials having flexibility and a light-transmittingproperty include polyester resins such as PET and PEN, apolyacrylonitrile resin, an acrylic resin, a polyimide resin, apolymethyl methacrylate resin, a PC resin, a PES resin, polyamide resins(such as nylon and aramid), a polysiloxane resin, a cycloolefin resin, apolystyrene resin, a polyamide-imide resin, a polyurethane resin, apolyvinyl chloride resin, a polyvinylidene chloride resin, apolypropylene resin, a PTFE resin, and an ABS resin. In particular, amaterial with a low coefficient of linear expansion is preferred, andfor example, a polyamide imide resin, a polyimide resin, a polyamideresin, or PET can be suitably used. A substrate in which a fibrous bodyis impregnated with a resin, a substrate whose linear thermal expansioncoefficient is reduced by mixing an inorganic filler with a resin, orthe like can also be used.

The flexible substrate may have a stacked-layer structure in which atleast one of a hard coat layer (e.g., a silicon nitride layer) by whicha surface of the device is protected from damage, a layer for dispersingpressure (e.g., an aramid resin layer), and the like is stacked over alayer of any of the above-mentioned materials. A substrate that can beused as the protective substrate 132 may be used.

When a glass layer is used for the flexible substrate, a barrierproperty against water and oxygen can be improved and thus a highlyreliable display panel can be provided.

For the bonding layer, various curable adhesives such as a photocurableadhesive (e.g., an ultraviolet curable adhesive), a reactive curableadhesive, a thermosetting adhesive, and an anaerobic adhesive can beused. Alternatively, an adhesive sheet or the like may be used.

Furthermore, the bonding layer may include a drying agent. For example,it is possible to use a substance that adsorbs moisture by chemicaladsorption, such as oxide of an alkaline earth metal (e.g., calciumoxide or barium oxide). Alternatively, it is possible to use a substancethat adsorbs moisture by physical adsorption, such as zeolite or silicagel. The drying agent is preferably included because entry of impuritiessuch as moisture into the functional element can be suppressed, therebyimproving the reliability of the display panel.

When a filler with a high refractive index or a light scattering memberis contained in the bonding layer, the efficiency of light extractionfrom the light-emitting element can be improved. For example, titaniumoxide, barium oxide, zeolite, or zirconium can be used.

As the light-emitting element, a self-luminous element can be used, andan element whose luminance is controlled by current or voltage isincluded in the category of the light-emitting element. For example, alight-emitting diode (LED), an organic EL element, an inorganic ELelement, or the like can be used. Any of a variety of display elementscan be used in the display panel of one embodiment of the presentinvention. For example, a liquid crystal element, an electrophoreticelement, a display element using MEMS, or the like may be used.

The light-emitting element may be a top-emission, bottom-emission, ordual-emission light-emitting element. A conductive film that transmitsvisible light is used as the electrode through which light is extracted.A conductive film that reflects visible light is preferably used as theelectrode through which light is not extracted.

The structure of the transistors in the display panel is notparticularly limited. For example, a planar transistor, a forwardstaggered transistor, or an inverted staggered transistor may be used. Atop-gate transistor or a bottom-gate transistor may be used. Gateelectrodes may be provided above and below a channel.

There is no particular limitation on the crystallinity of asemiconductor material used for the transistors, and an amorphoussemiconductor or a semiconductor having crystallinity (amicrocrystalline semiconductor, a polycrystalline semiconductor, asingle crystal semiconductor, or a semiconductor partly includingcrystal regions) may be used. It is preferable that a semiconductorhaving crystallinity be used, in which case deterioration of thetransistor characteristics can be suppressed.

A semiconductor material used for the transistor is not particularlylimited, and for example, a Group 14 element, a compound semiconductor,or an oxide semiconductor can be used. Typically, a semiconductorcontaining silicon, a semiconductor containing gallium arsenide, anoxide semiconductor containing indium, or the like can be used.

An oxide semiconductor is preferably used as a semiconductor where achannel of the transistor is formed. In particular, an oxidesemiconductor having a wider band gap than silicon is preferably used. Asemiconductor material having a wider band gap and a lower carrierdensity than silicon is preferably used because off-state current of thetransistor can be reduced.

For example, the oxide semiconductor preferably contains at least indium(In) or zinc (Zn). Further preferably, the oxide semiconductor containsan oxide represented by an In-M-Zn oxide (M is a metal such as Al, Ti,Ga, Ge, Y, Zr, Sn, La, Ce, Hf, or Nd).

An organic insulating material or an inorganic insulating material canbe used for the insulating layers included in the display panel.Examples of resins include an acrylic resin, an epoxy resin, a polyimideresin, a polyamide resin, a polyimide-amide resin, a siloxane resin, abenzocyclobutene-based resin, and a phenol resin. Examples of inorganicinsulating films include a silicon oxide film, a silicon oxynitridefilm, a silicon nitride oxide film, a silicon nitride film, an aluminumoxide film, a hafnium oxide film, an yttrium oxide film, a zirconiumoxide film, a gallium oxide film, a tantalum oxide film, a magnesiumoxide film, a lanthanum oxide film, a cerium oxide film, and a neodymiumoxide film.

The conductive layers included in the display panel can each have asingle-layer structure or a stacked-layer structure including any ofmetals such as aluminum, titanium, chromium, nickel, copper, yttrium,zirconium, molybdenum, silver, tantalum, and tungsten or an alloycontaining any of these metals as its main component. Alternatively, alight-transmitting conductive material such as indium oxide, ITO, indiumoxide containing tungsten, indium zinc oxide containing tungsten, indiumoxide containing titanium, ITO containing titanium, indium zinc oxide,ZnO, ZnO to which gallium is added, or indium tin oxide containingsilicon may be used. Alternatively, a semiconductor such as an oxidesemiconductor or polycrystalline silicon whose resistance is lowered bycontaining an impurity element or the like, or silicide such as nickelsilicide may be used. A film including graphene may be used as well. Thefilm including graphene can be formed, for example, by reducing a filmcontaining graphene oxide. A semiconductor such as an oxidesemiconductor containing an impurity element may be used. Alternatively,the conductive layers may be formed using a conductive paste of silver,carbon, copper, or the like or a conductive polymer such as apolythiophene. A conductive paste is preferable because it isinexpensive. A conductive polymer is preferable because it is easilyapplied.

FIG. 15 is an example of a cross-sectional view of a display deviceincluding two display panels 370 illustrated in FIG. 14C that overlapwith each other.

FIG. 15 illustrates the display region 101 a (corresponding to thedisplay portion 381 in FIG. 14C) and the region 120 a blocking visiblelight (corresponding to the driver circuit portion 382 and the like inFIG. 14C) of a lower display panel, and the display region 101 b(corresponding to the display portion 381 in FIG. 14C) and the region110 b transmitting visible light (corresponding to the region 110transmitting visible light in FIG. 14C) of an upper display panel.

In the display device illustrated in FIG. 15, the display panelpositioned on the display surface side (upper side) includes the region110 b transmitting visible light adjacent to the display region 101 b.The display region 101 a of the lower display panel and the region 110 btransmitting visible light of the upper display panel overlap with eachother. Thus, a non-display region between the display regions of the twodisplay panels overlapping with each other can be reduced or evenremoved. Accordingly, a large display device in which a seam betweendisplay panels is less likely to be noticed by a user can be obtained.

The display device illustrated in FIG. 15 includes thelight-transmitting layer 103 having a refractive index higher than thatof air and transmitting visible light between the display region 101 aand the region 110 b transmitting visible light. In that case, air canbe prevented from entering between the display region 101 a and theregion 110 b transmitting visible light, so that the interfacereflection due to a difference in refractive index can be reduced. Inaddition, display unevenness or luminance unevenness of the displaydevice can be suppressed.

The light-transmitting layer 103 may overlap with the entire surface ofthe substrate 211 of the lower display panel or that of the substrate201 of the upper display panel, or may overlap with only the displayregion 101 a and the region 110 b transmitting visible light. Inaddition, the light-transmitting layer 103 may overlap with the region120 a blocking visible light.

Modification Example

FIG. 16 is a cross-sectional view of a display panel 370B employing aseparate coloring method and having a top-emission structure.

The display panel 370B is different from the display panel 370A in thatthe insulating layer 215 is provided in contact with the light-emittingelement 304 and that the substrate 211 is bonded with not the bondinglayer 213 but the bonding layer 317.

In manufacturing the display panel 370A, the insulating layer 215 formedover a formation substrate is transferred to the substrate 201. Incontrast, in manufacturing the display panel 370B, the insulating layer215 is directly formed on the light-emitting element 304. This structureeliminates the need for the peeling process, which simplifies themanufacturing process of the display panel.

Example 2 of Cross-Sectional Structure of Display Panel

FIG. 17 is a cross-sectional view of a display panel 370C employing acolor filter method and having a top-emission structure. FIG. 18 is across-sectional view of a display panel 370D employing a color filtermethod and having a bottom-emission structure.

The display panel 370C is different from the display panel 370A in thatthe EL layer 322 is shared by a plurality of light-emitting elements,each transistor does not include a back gate, and a coloring layer 325and a light-blocking layer 326 are provided.

The display panel 370D is different from the display panel 370A in thatthe EL layer 322 is shared by a plurality of light-emitting elements,each transistor does not include a back gate, and the coloring layer 325is provided.

In each of the display panel 370C and the display panel 370D, thelight-emitting element 304 emits light to the coloring layer 325 side.

Owing to the combination of a color filter (the coloring layer 325) anda microcavity structure (the optical adjustment layer 324), light withhigh color purity can be extracted from the display panel. The thicknessof the optical adjustment layer 324 is varied depending on the color ofthe pixel.

The coloring layer is a colored layer that transmits light in a specificwavelength range. For example, a color filter that transmits light in aspecific wavelength range, such as red, green, blue, or yellow light,can be used. Examples of materials that can be used for the coloringlayer include a metal material, a resin material, and a resin materialcontaining a pigment or dye.

The light-blocking layer is provided between the adjacent coloringlayers. The light-blocking layer blocks light emitted from an adjacentlight-emitting element to inhibit color mixture between adjacentlight-emitting elements. Here, the coloring layer is provided such thatits end portion overlaps with the light-blocking layer, whereby lightleakage can be reduced. For the light-blocking layer, a material thatblocks light from the light-emitting element can be used; for example, ablack matrix can be formed using a metal material or a resin materialcontaining a pigment or dye. Note that it is preferable to provide thelight-blocking layer in a region other than a pixel portion, such as adriver circuit, in which case undesired leakage of guided light or thelike can be suppressed.

A display panel may include an overcoat. The overcoat can preventimpurities and the like contained in the coloring layer 325 from beingdiffused into the light-emitting element 304. The overcoat is formedusing a material that transmits light emitted from the light-emittingelement 304. For example, it is possible to use an inorganic insulatingfilm such as a silicon nitride film or a silicon oxide film, an organicinsulating film such as an acrylic film or a polyimide film, or astacked layer of an organic insulating film and an inorganic insulatingfilm.

<Touch Panel>

In one embodiment of the present invention, a display panel providedwith a touch sensor (also referred to as an input/output unit or a touchpanel) can be manufactured.

There is no particular limitation on a sensor element included in thetouch panel of one embodiment of the present invention. Note that avariety of sensors that can sense proximity or touch of a sensing targetsuch as a finger or a stylus can be used as the sensor element.

For example, a variety of types such as a capacitive type, a resistivetype, a surface acoustic wave type, an infrared type, an optical type,and a pressure-sensitive type can be used for the sensor.

In this embodiment, a touch panel including a capacitive sensor elementis described as an example.

Examples of the capacitive sensor element include a surface capacitivesensor element and a projected capacitive sensor element. Examples ofthe projected capacitive sensor element include a self-capacitive sensorelement and a mutual capacitive sensor element. The use of a mutualcapacitive sensor element is preferable because multiple points can besensed simultaneously.

The touch panel of one embodiment of the present invention can have anyof a variety of structures, including a structure in which a displaypanel and a sensor element that are separately formed are attached toeach other and a structure in which an electrode and the like includedin a sensor element are provided on one or both of a substratesupporting a display element and a counter substrate.

FIG. 19A is a schematic perspective view of a touch panel 300. FIG. 19Bis a developed view of the schematic perspective view of FIG. 19A. Notethat only typical components are illustrated for simplicity. In FIG.19B, some components (such as a substrate 261 and the substrate 211) areillustrated only in dashed outline.

The touch panel 300 includes an input device 310 and the display panel370, which are provided to overlap with each other. The touch panel 300includes the region 110 transmitting visible light. The region 110transmitting visible light is adjacent to the display portion 381 andprovided along two sides of the display portion 381.

The input device 310 includes the substrate 261, an electrode 331, anelectrode 332, a plurality of wirings 341, and a plurality of wirings342. An FPC 350 is electrically connected to each of the plurality ofwirings 341 and the plurality of wirings 342. The FPC 350 is providedwith an IC 351.

The display panel 370 includes the substrate 201 and the substrate 211that are provided so as to face each other. The display panel 370includes the display portion 381 and the driver circuit portion 382. Awiring 383 and the like are provided over the substrate 201. The FPC 373is electrically connected to the wiring 383. The FPC 373 is providedwith an IC 374.

The wiring 383 has a function of supplying a signal and power to thedisplay portion 381 and the driver circuit portion 382. The signal andpower are each input to the wiring 383 from the outside or the IC 374through the FPC 373.

FIG. 20 shows an example of a cross-sectional view of the touch panel300. FIG. 20 illustrates cross-sectional structures of the displayportion 381, the driver circuit portion 382, the region 110 transmittingvisible light, the region including the FPC 373, the region includingthe FPC 350, and the like. Furthermore, FIG. 20 illustrates across-sectional structure of a crossing portion 387 where a wiringformed by processing a conductive layer used for forming the gate of thetransistor and a wiring formed by processing a conductive layer used forforming the source and the drain of the transistor cross each other.

The substrate 201 and the substrate 211 are attached to each other withthe bonding layer 317. The substrate 211 and the substrate 261 areattached to each other with a bonding layer 396. Here, the layers fromthe substrate 201 to the substrate 211 correspond to the display panel370. Furthermore, the layers from the substrate 261 to an electrode 334correspond to the input device 310. In other words, the bonding layer396 attaches the display panel 370 and the input device 310 to eachother. Alternatively, the layers from the substrate 201 to theinsulating layer 215 correspond to the display panel 370. Furthermore,the layers from the substrate 261 to the substrate 211 correspond to theinput device 310. In other words, the bonding layer 213 attaches thedisplay panel 370 and the input device 310 to each other.

The display panel 370 in FIG. 20 is different from the display panel370A in FIG. 14C in the structures of the transistors 301, 302, and 303and the capacitor 305.

Each transistor includes a gate, the gate insulating layer 311, asemiconductor layer, a source, and a drain. The gate and thesemiconductor layer overlap with each other with the gate insulatinglayer 311 provided therebetween. The semiconductor layer may includelow-resistance regions 348. The low-resistance regions 348 function asthe source and drain of the transistor.

The conductive layer over the insulating layer 313 functions as a leadwiring. The conductive layer is electrically connected to the region 348through an opening provided in the insulating layer 313, the insulatinglayer 312, and the gate insulating layer 311.

In FIG. 20, the capacitor 305 has a stacked-layer structure thatincludes a layer formed by processing a semiconductor layer used forforming the above-described semiconductor layer, the gate insulatinglayer 311, and a layer formed by processing a conductive layer used forforming the gate. Here, part of the semiconductor layer of the capacitor305 preferably has a region 349 having a higher conductivity than aregion 347 where the channel of the transistor is formed.

The region 348 and the region 349 each can be a region containing moreimpurities than the region 347 where the channel of the transistor isformed, a region with a high carrier concentration, a region with lowcrystallinity, or the like.

On the substrate 211 side of the substrate 261, the electrode 331 andthe electrode 332 are provided. An example where the electrode 331includes an electrode 333 and the electrode 334 is described here. Asillustrated in the crossing portion 387 in FIG. 20, the electrodes 332and 333 are formed on the same plane. An insulating layer 395 isprovided to cover the electrode 332 and the electrode 333. The electrode334 electrically connects two electrodes 333, between which theelectrode 332 is provided, through openings formed in the insulatinglayer 395.

In a region near the end portion of the substrate 261, a connectionportion 308 is provided. The connection portion 308 has a stack of awiring 342 and a conductive layer formed by processing a conductivelayer used for forming the electrode 334. The connection portion 308 iselectrically connected to the FPC 350 through a connector 309.

The input device 310 has a structure in which the reflection of light inthe region 110 transmitting visible light is suppressed. The insulatinglayer 395 is provided in the display portion 381 and is not provided inthe region 110 transmitting visible light.

The region 110 transmitting visible light of the touch panel 300includes the substrate 201, the bonding layer 203, the insulating layer205, the gate insulating layer 311, the insulating layer 312, theinsulating layer 314, the bonding layer 317, the insulating layer 215,the bonding layer 213, the substrate 211, the bonding layer 396, theinsulating layer 393, and the substrate 261 that are stacked in thisorder.

Even in the case where two or more touch panels 300 overlap with eachother, an area in which a plurality of touch panels 300 overlap witheach other (overlapping area) is less likely to be noticed by a user ofthe touch panel. In addition, the difference in the luminance of displayon the display portion 381 between a portion seen through the region 110transmitting visible light and a portion seen not through the region canbe small.

FIGS. 21A and 21B are schematic perspective views of a touch panel 320.

The touch panel 320 includes the region 110 transmitting visible light.The region 110 transmitting visible light is adjacent to the displayportion 381 and provided along two sides of the display portion 381.

In FIGS. 21A and 21B, the substrate 211 of a display panel 379 isprovided with an input device 318. The wiring 341, the wiring 342, andthe like of the input device 318 are electrically connected to the FPC350 provided for the display panel 379.

With the above structure, the FPC connected to the touch panel 320 canbe provided only on one substrate side (on the substrate 201 side inthis embodiment). FIGS. 21A and 21B illustrate the structure in whichthe touch panel 320 is provided with two FPCs. The touch panel 320 isnot necessarily provided with a plurality of FPCs. When the touch panel320 is provided with one FPC and signals are supplied to both thedisplay panel 379 and the input device 318, the structure can besimplified.

The IC 374 has a function of driving the display panel 379. The IC 351has a function of driving the input device 318.

This embodiment can be combined with any of other embodiments asappropriate.

Embodiment 4

In this embodiment, electronic devices and lighting devices ofembodiments of the present invention are described with reference todrawings.

Examples of electronic devices include a television set, a monitor of acomputer or the like, a digital camera, a digital video camera, adigital photo frame, a mobile phone (also referred to as a mobile phonedevice), a portable game machine, a portable information terminal, anaudio reproducing device, a large game machine such as a pinballmachine, and the like.

The electronic device or the lighting device of one embodiment of thepresent invention has flexibility and therefore can be incorporatedalong a curved inside/outside wall surface of a house or a building or acurved interior/exterior surface of a car.

Furthermore, the electronic device of one embodiment of the presentinvention may include a secondary battery. It is preferable that thesecondary battery be capable of being charged by non-contact powertransmission.

Examples of the secondary battery include a lithium ion secondarybattery such as a lithium polymer battery using a gel electrolyte(lithium ion polymer battery), a nickel-hydride battery, anickel-cadmium battery, an organic radical battery, a lead-acid battery,an air secondary battery, a nickel-zinc battery, and a silver-zincbattery.

The electronic device of one embodiment of the present invention mayinclude an antenna. When a signal is received by the antenna, theelectronic device can display an image, data, or the like on a displayportion. When the electronic device includes the antenna and a secondarybattery, the antenna may be used for contactless power transmission.

In the display device of one embodiment of the present invention, thearea of the display region can be increased unlimitedly by increasingthe number of display panels. Thus, the display device of one embodimentof the present invention can be favorably used for digital signage, aPID, or the like. Furthermore, the shape of the display region of thedisplay device of one embodiment of the present invention can be changedvariously when the arrangement of the display panels is changed.

FIG. 22A illustrates an example in which a display device 10 of oneembodiment of the present invention is provided for each of pillars 15and walls 16. A flexible display panel is used as a display panelincluded in the display device 10, whereby the display device 10 can beplaced along a curved surface.

Here, in particular, in the case where the display device of oneembodiment of the present invention is used in digital signage or a PID,it is preferable to use a touch panel in a display panel because adevice with such a structure does not just display a still or movingimage on a display region, but can be operated by viewers intuitively.Alternatively, in the case where the display device of one embodiment ofthe present invention is used for providing information such as routeinformation or traffic information, usability can be enhanced byintuitive operation. In the case of providing the display device on thewalls of buildings, public facilities, or the like, a touch panel doesnot need to be used in the display panel.

FIGS. 22B to 22E illustrate examples of an electronic device including adisplay portion 7000 with a curved surface. The display surface of thedisplay portion 7000 is bent, and images can be displayed on the bentdisplay surface. The display portion 7000 may be flexible.

The display portion 7000 of each of the electronic devices illustratedin FIGS. 22B to 22E can be formed using the display device of oneembodiment of the present invention.

FIG. 22B illustrates an example of a mobile phone. A mobile phone 7100includes a housing 7101, the display portion 7000, operation buttons7103, an external connection port 7104, a speaker 7105, a microphone7106, and the like.

The mobile phone 7100 illustrated in FIG. 22B includes a touch sensor inthe display portion 7000. Moreover, operations such as making a call andinputting a letter can be performed by touch on the display portion 7000with a finger, a stylus, or the like.

With the operation buttons 7103, the power can be turned on or off. Inaddition, types of images displayed on the display portion 7000 can beswitched; for example, switching images from a mail creation screen to amain menu screen is performed with the operation button 7103.

FIG. 22C illustrates an example of a television set. In a television set7200, the display portion 7000 is incorporated into a housing 7201.Here, the housing 7201 is supported by a stand 7203.

The television set 7200 illustrated in FIG. 22C can be operated with anoperation switch of the housing 7201 or a separate remote controller7211. Furthermore, the display portion 7000 may include a touch sensor,and can be operated by touch on the display portion 7000 with a fingeror the like. Furthermore, the remote controller 7211 may be providedwith a display portion for displaying data output from the remotecontroller 7211. With operation keys or a touch panel of the remotecontroller 7211, channels and volume can be controlled and imagesdisplayed on the display portion 7000 can be controlled.

Note that the television set 7200 is provided with a receiver, a modem,or the like. A general television broadcast can be received with thereceiver. Furthermore, when the television set is connected to acommunication network with or without wires via modem, one-way (from atransmitter to a receiver) or two-way (between a transmitter and areceiver or between receivers) data communication can be performed.

FIG. 22D illustrates an example of a portable information terminal. Aportable information terminal 7300 includes a housing 7301 and thedisplay portion 7000. The portable information terminal may also includean operation button, an external connection port, a speaker, amicrophone, an antenna, a battery, or the like. The display portion 7000is provided with a touch sensor. An operation of the portableinformation terminal 7300 can be performed by touching the displayportion 7000 with a finger, a stylus, or the like.

FIG. 22D is a perspective view of the portable information terminal7300. FIG. 22E is a top view of the portable information terminal 7300.

Each of the portable information terminals illustrated in thisembodiment functions as, for example, one or more of a telephone set, anotebook, and an information browsing system. Specifically, each of theportable information terminals can be used as a smartphone. Each of theportable information terminals illustrated in this embodiment is capableof executing a variety of applications such as mobile phone calls,e-mailing, reading and editing texts, music reproduction, Internetcommunication, and a computer game, for example.

The portable information terminal 7300 can display letters or an imageon its plurality of surfaces. For example, as illustrated in FIG. 22D,three operation buttons 7302 can be displayed on one surface, andinformation 7303 indicated by a rectangle can be displayed on anothersurface. FIGS. 22D and 22E illustrate an example in which information isdisplayed at the top of the portable information terminal.Alternatively, information may be displayed on the side of the portableinformation terminal. Information may also be displayed on three or moresurfaces of the portable information terminal.

Examples of the information include notification from a socialnetworking service (SNS), display indicating reception of an e-mail oran incoming call, the title of an e-mail or the like, the sender of ane-mail or the like, the date, the time, remaining battery, and thereception strength of an antenna. Alternatively, the operation button,an icon, or the like may be displayed in place of the information.

For example, a user of the portable information terminal 7300 can seethe display (here, the information 7303) with the portable informationterminal 7300 put in a breast pocket of his/her clothes.

Specifically, a caller's phone number, name, or the like of an incomingcall is displayed in a position that can be seen from above the portableinformation terminal 7300. Thus, the user can see the display withouttaking out the portable information terminal 7300 from the pocket anddecide whether to answer the call.

FIG. 22F illustrates an example of a lighting device having a curvedlight-emitting portion.

The light-emitting portion included in the lighting device illustratedin FIG. 22F can be manufactured using the display device of oneembodiment of the present invention.

A lighting device 7400 illustrated in FIG. 22F includes a light-emittingportion 7402 having a wave-shaped light-emitting surface, which is agood-design lighting device.

The light-emitting portion included in the lighting device 7400 may beflexible. The light-emitting portion may be fixed on a plastic member, amovable frame, or the like so that a light-emitting surface of thelight-emitting portion can be bent freely depending on the intended use.

The lighting device 7400 includes a stage 7401 provided with anoperation switch 7403 and a light-emitting portion supported by thestage 7401.

Note that although the lighting device in which the light-emittingportion is supported by the stage is described as an example here, ahousing provided with a light-emitting portion can be fixed on a ceilingor suspended from a ceiling. Since the light-emitting surface can becurved, the light-emitting surface is curved to have a depressed shape,whereby a particular region can be brightly illuminated, or thelight-emitting surface is curved to have a projecting shape, whereby awhole room can be brightly illuminated.

FIGS. 23A1, 23A2, and 23B to 23I illustrate examples of portableinformation terminals including a display portion 7001 havingflexibility.

The display portion 7001 is manufactured using the display device of oneembodiment of the present invention. For example, a display deviceincluding a display panel that can be bent with a radius of curvature ofgreater than or equal to 0.01 mm and less than or equal to 150 mm can beused. The display portion 7001 may include a touch sensor so that theportable information terminal can be operated by touching the displayportion 7001 with a finger or the like.

FIGS. 23A1 and 23A2 are a perspective view and a side view,respectively, illustrating an example of the portable informationterminal. A portable information terminal 7500 includes a housing 7501,the display portion 7001, a display portion tab 7502, operation buttons7503, and the like.

The portable information terminal 7500 includes a rolled flexibledisplay portion 7001 in the housing 7501.

The portable information terminal 7500 can receive a video signal with acontrol portion incorporated therein and can display the received videoon the display portion 7001. The portable information terminal 7500incorporates a battery. A terminal portion for connecting a connectormay be included in the housing 7501 so that a video signal or power canbe directly supplied from the outside with a wiring.

By pressing the operation buttons 7503, power on/off, switching ofdisplayed images, and the like can be performed. Although FIGS. 23A1,23A2, and 23B illustrate an example where the operation buttons 7503 arepositioned on a side surface of the portable information terminal 7500,one embodiment of the present invention is not limited thereto. Theoperation buttons 7503 may be placed on a display surface (a frontsurface) or a rear surface of the portable information terminal 7500.

FIG. 23B illustrates the portable information terminal 7500 in a statewhere the display portion 7001 is pulled out. Images can be displayed onthe display portion 7001 in this state. The display portion 7001 can beextracted with the use of the display portion tab 7502. In addition, theportable information terminal 7500 may perform different displays in thestate where part of the display portion 7001 is rolled as illustrated inFIG. 23A1 and in the state where the display portion 7001 is pulled outas illustrated in FIG. 23B. For example, in the state illustrated inFIG. 23A1, the rolled portion of the display portion 7001 is put in anon-display state, which results in a reduction in power consumption ofthe portable information terminal 7500.

Note that a reinforcement frame may be provided for a side portion ofthe display portion 7001 so that the display portion 7001 has a flatdisplay surface when pulled out.

Note that in addition to this structure, a speaker may be provided forthe housing so that sound is output with an audio signal receivedtogether with a video signal.

FIGS. 23C to 23E illustrate an example of a foldable portableinformation terminal. FIG. 23C illustrates a portable informationterminal 7600 that is opened. FIG. 23D illustrates the portableinformation terminal 7600 that is being opened or being folded. FIG. 23Eillustrates the portable information terminal 7600 that is folded. Theportable information terminal 7600 is highly portable when folded, andis highly browsable when opened because of a seamless large displayarea.

A display portion 7001 is supported by three housings 7601 joinedtogether by hinges 7602. By folding the portable information terminal7600 at a connection portion between two housings 7601 with the hinges7602, the portable information terminal 7600 can be reversibly changedin shape from an opened state to a folded state.

FIGS. 23F and 23G illustrate an example of a foldable portableinformation terminal. FIG. 23F illustrates a portable informationterminal 7650 that is folded so that the display portion 7001 is on theinside. FIG. 23G illustrates the portable information terminal 7650 thatis folded so that the display portion 7001 is on the outside. Theportable information terminal 7650 includes the display portion 7001 anda non-display portion 7651. When the portable information terminal 7650is not used, the portable information terminal 7650 is folded so thatthe display portion 7001 is on the inside, whereby contamination of ordamage to the display portion 7001 can be suppressed.

FIG. 23H illustrates an example of a flexible portable informationterminal. A portable information terminal 7700 includes a housing 7701and the display portion 7001. In addition, the portable informationterminal 7700 may include buttons 7703 a and 7703 b that serve as inputmeans, speakers 7704 a and 7704 b that serve as sound output means, anexternal connection port 7705, a microphone 7706, or the like. Aflexible battery 7709 can be mounted on the portable informationterminal 7700. The battery 7709 may overlap with the display portion7001, for example.

The housing 7701, the display portion 7001, and the battery 7709 areflexible. Thus, it is easy to curve the portable information terminal7700 into a desired shape or to twist the portable information terminal7700. For example, the portable information terminal 7700 can be curvedso that the display portion 7001 is on the inside or in the outside. Theportable information terminal 7700 can be used in a rolled state. Sincethe housing 7701 and the display portion 7001 can be transformed freelyin this manner, the portable information terminal 7700 is less likely tobe broken even when the portable information terminal 7700 falls down orexternal stress is applied to the portable information terminal 7700.

The portable information terminal 7700 can be used effectively invarious situations because the portable information terminal 7700 islightweight. For example, the portable information terminal 7700 can beused in the state where the upper portion of the housing 7701 issuspended by a clip or the like, or in the state where the housing 7701is fixed to a wall by magnets or the like.

FIG. 23I illustrates an example of a wrist-watch-type portableinformation terminal. A portable information terminal 7800 includes aband 7801, the display portion 7001, an input-output terminal 7802,operation buttons 7803, or the like. The band 7801 has a function of ahousing. A flexible battery 7805 can be mounted on the portableinformation terminal 7800. The battery 7805 may overlap with the displayportion 7001 or the band 7801, for example.

The band 7801, the display portion 7001, and the battery 7805 haveflexibility. Thus, the portable information terminal 7800 can be easilycurved to have a desired shape.

With the operation button 7803, a variety of functions such as timesetting, on/off of the power, on/off of wireless communication, settingand cancellation of silent mode, and setting and cancellation of powersaving mode can be performed. For example, the functions of theoperation button 7803 can be set freely by the operating systemincorporated in the portable information terminal 7800.

By touching an icon 7804 displayed on the display portion 7001 with afinger or the like, application can be started.

The portable information terminal 7800 can employ near fieldcommunication that is a communication method based on an existingcommunication standard. In that case, for example, mutual communicationbetween the portable information terminal 7800 and a headset capable ofwireless communication can be performed, and thus hands-free calling ispossible.

The portable information terminal 7800 may include the input-outputterminal 7802. In the case where the input-output terminal 7802 isincluded, data can be directly transmitted to and received from anotherinformation terminal via a connector. Charging through the input-outputterminal 7802 is also possible. Note that charging of the portableinformation terminal described as an example in this embodiment can beperformed by non-contact power transmission without using theinput-output terminal.

Next, a display device of one embodiment of the present invention thatcan be used for a display portion having a curved surface is described.FIGS. 24A and 24B are a top view and a side view illustrating a displaydevice that includes four display panels arranged in a 2×2 matrix.

The display panels illustrated in FIG. 24A each include a light-emittingportion 250, a demultiplexer 253 functioning as a source driver, a scandriver 255, and the like. Two sides of the light-emitting portion 250are in contact with a region 251 transmitting visible light. A leadwiring 257 is provided along the other two sides.

The display device illustrated in FIGS. 24A and 24B is formed byoverlapping a plurality of display panels so that a non-display regionbetween display regions is small. A light-transmitting layer (e.g., anadhesive) may be provided between the region 251 transmitting visiblelight of an upper display panel and the light-emitting portion 250 of alower display panel.

A component that blocks visible light such as a lead wiring or a driveris not provided at all from an end portion of the light-emitting portion250 to an end portion of the display panel along two sides of thedisplay panel, and the region along two sides serves as the region 251transmitting visible light. The thickness of the region 251 transmittingvisible light (which can be regarded as the thickness of one displaypanel) is very small (for example, the thickness can be greater than orequal to 100 μm and less than or equal to 1000 μm). Therefore, althoughthe display device in this embodiment has a region in which at most fourdisplay panels overlap with each other, a step formed on the displaysurface side is extremely small; thus, a seam hardly stands out.

The four display panels have flexibility. As illustrated in FIG. 24B,the light-emitting portion 250 of the display panel is gently curved.The region near the FPC 373, which is illustrated as a region R in FIG.24B, is curved with a smaller radius of curvature than thelight-emitting portion 250. As a result, the FPC 373 can be placedwithout physical interference with the rear surface of the upper displaypanel. In this way, another display panel can be provided on four sidesof the display panel, whereby a large-sized display device is easilyrealized.

The radius of curvature of the region near the FPC 373 (i.e., the regionwhere the light-emitting portion 250 is not provided) can be, forexample, greater than or equal to 1 mm and less than or equal to 100 mm.The radius of curvature of the light-emitting portion 250 can be largerthan that of the region near the FPC 373 and smaller than or equal to10000 mm, and may be larger than or equal to 10 mm and smaller than orequal to 10000 mm, for example.

The display panel 100 in FIG. 24B is attached to one plane of a support376 (e.g., a metal plate). The support 376 has a plurality of curvedsurfaces, and the display panel 100 is curved along the curved surfaces.The display panel 100 has a portion extending from the support 376. Theportion overlaps with an adjacent display panel 100. A driver circuit orthe like may be fixed on the other plane of the support 376. In thatcase, the display panel 100 is electrically connected to the drivercircuit with the FPC 373.

The optical member 240 is preferably provided on the display surfaceside of the display panel as illustrated in FIG. 24B. The optical member240 is preferably fixed on a housing or the like with the optical member240 and the display panel being in intimate contact with each other. Theoptical member 240 consists of, for example, a support, a circularlypolarizing plate, and an anti-reflection member from the display panelside.

This embodiment can be combined with any of other embodiments asappropriate.

Example 1

In this example, element structures and properties of light-emittingelements that can be used in one embodiment of the present inventionwill be described. Note that FIG. 25 illustrates an element structure oflight-emitting elements described in this example, and Table 1 showsspecific structures. Chemical formulae of materials used in this exampleare shown below.

TABLE 1 Light- Electron- First Hole-injection Hole-transport emittingElectron-transport injection electrode layer layer layer layer layerSecond electrode Light- APC\ PCPPn:MoOx PCPPn PCBBiF * 2mDBTBPDBq-IINBphen LiF Ag:Mg ITO emitting ITSO (1:0.5) (15 nm) (55 nm) (10 nm) (10nm) (1 nm) (1:0.1) (70 nm) element (110 nm)   (20 nm) (25 nm) 1(R)Light- APC\ PCPPn:MoOx PCPPn PCBBiF ** 2mDBTBPDBq-II NBphen LiF Ag:MgITO emitting ITSO (1:0.5) (15 nm) (35 nm) (10 nm) (10 nm) (1 nm) (1:0.1)(70 nm) element (110 nm)  (7.5 nm) (25 nm) 2(G) Light- APC\ PCPPn:MoOxPCPPn *** 2mDBTBPDBq-II NBphen LiF Ag:Mg ITO emitting ITSO (1:0.5) (15nm) (10 nm) (10 nm) (1 nm) (1:0.1) (70 nm) element (110 nm) (17.5 nm)(25 nm) 3(B) * 2mDBTBPDBq-II:PCBBiF:[Ir(dmdppr-P)₂(dibm)] (0.8:0.2:0.06(70 nm)) ** 2mDBTBPDBq-II:PCBBiF:[Ir(tBuppm)₃] (0.8:0.2:0.06 (40 nm))*** cgDBCzPA:1,6BnfAPrn-03 (1:0.03 (25 nm))

<<Fabrication of Light-Emitting Elements>>

The light-emitting elements described in this example each included, asillustrated in FIG. 25, a first electrode 1901 over a substrate 1900, anEL layer 1902 over the first electrode 1901, and a second electrode 1903over the EL layer 1902. In the EL layer 1902, a hole-injection layer1911, a hole-transport layer 1912, a light-emitting layer 1913, anelectron-transport layer 1914, and an electron-injection layer 1915 werestacked in this order from the first electrode 1901 side. Note that alight-emitting element 1 in this example was a light-emitting elementemitting mainly red light and is also referred to as a light-emittingelement 1(R). A light-emitting element 2 was a light-emitting elementemitting mainly green light and is also referred to as a light-emittingelement 2(G). A light-emitting element 3 was a light-emitting elementemitting mainly blue light and is also referred to as a light-emittingelement 3(B).

First, the first electrode 1901 was formed over the substrate 1900. Theelectrode area was set to 4 mm² (2 mm×2 mm). A glass substrate was usedas the substrate 1900. The first electrode 1901 was formed in thefollowing manner: an alloy film of silver (Ag), palladium (Pd), andcopper (Cu) (an Ag—Pd—Cu (APC) film) was formed to a thickness of 200 nmby a sputtering method, and an ITSO film was formed to a thickness of110 nm by a sputtering method. In this example, the first electrode 1901functioned as an anode. The first electrode 1901 was a reflectiveelectrode having a function of reflecting light.

As pretreatment, a surface of the substrate was washed with water,baking was performed at 200° C. for one hour, and then UV ozonetreatment was performed for 370 seconds. After that, the substrate wastransferred into a vacuum evaporation apparatus where the pressure hadbeen reduced to approximately 10⁻⁴ Pa, and was subjected to vacuumbaking at 170° C. for 60 minutes in a heating chamber of the vacuumevaporation apparatus, and then the substrate was cooled down for about30 minutes.

Next, the hole-injection layer 1911 was formed over the first electrode1901. After the pressure in the vacuum evaporation apparatus was reducedto 10⁻⁴ Pa, the hole-injection layer 1911 was formed by co-evaporationto have a weight ratio of3-[4-(9-phenanthryl)-phenyl]-9-phenyl-9H-carbazole (abbreviation: PCPPn)to molybdenum oxide of 1:0.5. The thickness of the hole-injection layer1911 was 20 nm in the light-emitting element 1(R), 7.5 nm in thelight-emitting element 2(G), and 17.5 nm in the light-emitting element3(B).

Then, the hole-transport layer 1912 was formed over the hole-injectionlayer 1911. In each of the light-emitting element 1(R), thelight-emitting element 2(G), and the light-emitting element 3(B), PCPPnwas deposited by evaporation to a thickness of 15 nm. In thelight-emitting element 1(R) and the light-emitting element 2(G),N-(1,1′-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF) was also deposited by evaporation. Thethickness of PCBBiF was 55 nm in the light-emitting element 1(R) and 35nm in the light-emitting element 2(G).

Next, the light-emitting layer 1913 was formed over the hole-transportlayer 1912.

As the light-emitting layer 1913 of the light-emitting element 1(R),2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mDBTBPDBq-II), PCBBiF, and bis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-κN]phenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-P)₂(dibm)]) were deposited by co-evaporationto a thickness of 70 nm such that the weight ratio of 2mDBTBPDBq-II toPCBBiF to [Ir(dmdppr-P)₂(dibm)] was 0.8:0.2:0.06.

As the light-emitting layer 1913 of the light-emitting element 2(G),2mDBTBPDBq-II, PCBBiF, andtris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation:[Ir(tBuppm)₃]) were deposited by co-evaporation to a thickness of 40 nmsuch that the weight ratio of 2mDBTBPDBq-II to PCBBiF to [Ir(tBuppm)₃]was 0.8:0.2:0.06.

As the light-emitting layer 1913 of the light-emitting element 3(B),7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole(abbreviation: cgDBCzPA) andN,N′-(pyrene-1,6-diyl)bis[(6,N-diphenylbenzo[b]naphtho[1,2-d]furan)-8-amine](abbreviation: 1,6BnfAPrn-03) were deposited by co-evaporation to athickness of 25 nm such that the weight ratio of cgDBCzPAto1,6BnfAPrn-03 was 1:0.03.

Next, the electron-transport layer 1914 was formed over thelight-emitting layer 1913. The electron-transport layer 1914 was formedin the following manner: 2mDBTBPDBq-II and2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation:NBphen) were sequentially deposited by evaporation to each have athickness of 10 nm.

Then, the electron-injection layer 1915 was formed over theelectron-transport layer 1914. As the electron-injection layer 1915,lithium fluoride (LiF) was deposited by evaporation to a thickness of 1nm.

Then, the second electrode 1903 was formed over the electron-injectionlayer 1915 in the following manner: silver (Ag) and magnesium (Mg) weredeposited by co-evaporation to a thickness of 25 nm at a volume ratio ofAg to Mg of 1:0.1, and then an indium tin oxide (ITO) was deposited to athickness of 70 nm by a sputtering method. In this example, the secondelectrode 1903 functioned as a cathode. Moreover, the second electrode1903 was a transflective electrode having functions of transmittinglight and reflecting light.

Through the above steps, the light-emitting elements in each of whichthe EL layer was provided between the pair of electrodes were eachformed over the substrate 1900. The hole-injection layer 1911, thehole-transport layer 1912, the light-emitting layer 1913, theelectron-transport layer 1914, and the electron-injection layer 1915described above were functional layers included in the EL layer of oneembodiment of the present invention. Furthermore, in all the evaporationsteps in the above fabrication method, evaporation was performed by aresistance-heating method.

Each of the light-emitting elements formed in this example was sealedbetween the substrate 1900 and a sealing substrate. The sealing betweenthe substrate 1900 and the sealing substrate was performed in such amanner that the sealing substrate was fixed to the substrate 1900 with asealing material in a glove box containing a nitrogen atmosphere, asealant was applied so as to surround the light-emitting element formedover the substrate 1900, and then irradiation with 365-nm ultravioletlight at 6 J/cm² was performed and heat treatment was performed at 80°C. for 1 hour.

The light-emitting elements formed in this example each had a structurein which light was emitted in the direction indicated by the arrow fromthe second electrode 1903 side of the light-emitting element.

The chromaticities (x, y) of the light-emitting elements formed in thisexample measured with a luminance colorimeter (BM-5AS manufactured byTOPCON CORPORATION) are shown in Table 2 below. The chromaticities ofthe light-emitting elements 1(R), 2(G), and 3(B) were measured atluminances of 1468 cd/m², 4329 cd/m², and 310 cd/m², respectively.

TABLE 2 Chromaticity Chromaticity coordinate x coordinate yLight-emitting 0.711 0.289 element 1 (R) Light-emitting 0.171 0.794element 2 (G) Light-emitting 0.142 0.036 element 3 (B)

The above results show that, in this example, the light-emitting element1(R) had a chromaticity coordinate x of greater than 0.680 and less thanor equal to 0.720 and a chromaticity coordinate y of greater than orequal to 0.260 and less than or equal to 0.320, the light-emittingelement 2(G) had a chromaticity coordinate x of greater than or equal to0.130 and less than or equal to 0.250 and a chromaticity coordinate y ofgreater than 0.710 and less than or equal to 0.810, and thelight-emitting element 3(B) had a chromaticity coordinate x of greaterthan or equal to 0.120 and less than or equal to 0.170 and achromaticity coordinate y of greater than or equal to 0.020 and lessthan 0.060. The light-emitting element 1(R) had a chromaticitycoordinate x of greater than 0.680 and thus had a better redchromaticity than the DCI-P3 standard. The light-emitting element 2(G)had a chromaticity coordinate y of greater than 0.710 and thus had abetter green chromaticity than the DCI-P3 standard and the NTSCstandard. In addition, the light-emitting element 3(B) had achromaticity coordinate y of less than 0.060 and thus had a better bluechromaticity than the DCI-P3 standard.

Although the chromaticities (x, y) of the light-emitting elementsobtained here were chromaticities on the CIE 1931 chromaticitycoordinates (x,y chromaticity coordinates), chromaticities on the CIE1976 chromaticity coordinates (u′,v′ chromaticity coordinates), whichare defined so that the perceived color differences may correspond todistances equivalent in the color space, can be obtained with the use ofthe following conversion equations (1).

$\begin{matrix}{\lbrack {{Formula}\mspace{14mu} 1} \rbrack\mspace{619mu}} & \; \\ \begin{matrix}{u^{\prime} = {4{x/( {{12y} - {2x} + 3} )}}} \\{v^{\prime} = {9{v/( {{12y} - {2x} + 3} )}}}\end{matrix} \} & (1)\end{matrix}$

The chromaticities of the light-emitting elements in this example on theCIE 1976 chromaticity coordinates (u′,v′ chromaticity coordinates) arelisted in Table 3 below. Table 4 shows the chromaticity coordinates inaccordance with the BT.2020 standard for comparison. In addition, FIG.26 shows a chromaticity diagram.

TABLE 3 Chromaticity Chromaticity coordinate u′ coordinate v′Light-emitting 0.563 0.516 element 1 (R) Light-emitting 0.056 0.586element 2 (G) Light-emitting 0.181 0.103 element 3 (B)

TABLE 4 Chromaticity Chromaticity coordinate u′ coordinate v′ BT.2020(R) 0.557 0.517 BT.2020 (G) 0.056 0.587 BT.2020 (B) 0.159 0.126

On the basis of the results in Table 3, the BT.2020 area ratio and theBT.2020 coverage calculated from the chromaticities (u′,v′) are 106% and97%, respectively. Note that an area A of a triangle formed byconnecting the CIE chromaticity coordinates (u′,v′) of RGB which fulfillthe BT.2020 standard and an area B of a triangle formed by connectingthe CIE chromaticity coordinates (u′,v′) of the three light-emittingelements in this example are calculated to obtain the area ratio (B/A).The coverage is a value which represents how much percentage of theBT.2020 standard color gamut (the inside of the above triangle) can bereproduced using a combination of the chromaticities of the threelight-emitting elements in this example.

In this example, the light-emitting element emitting red light, thatemitting green light, and that emitting blue light were fabricated. Thelight-emitting layers of these light-emitting elements were formed usingthe respective materials and the hole-transport layers were formed tohave the respective thicknesses in order to adjust the optical pathlengths. At the same time, in these light-emitting elements, theelectron-transport layers were formed using the same materials to havethe same thickness and the electron-injection layers were also formedusing the same material to have the same thickness; thus, thecombination of these light-emitting elements can reduce the number ofsteps as compared to that in the case where these layers are formed tohave structures different between the light-emitting elements. In thismanner, the three light-emitting elements achieve wide-range colorreproducibility despite the fact that many kinds of layers in the ELlayers each had a common structure between the light-emitting elements.Note that although the thickness of the hole-injection layer wasdifferent between the colors in this example, the hole-injection layersin the light-emitting elements for the three colors may have the samethickness.

In each of the light-emitting elements in this example for the threecolors, the same material was used for the layer that constituted thehole-transport layer and that was in contact with the hole-injectionlayer. The hole-transport layer in the light-emitting element 1(R) andthat in the light-emitting element 2(G) each included the PCPPn layerthat was in contact with the hole-injection layer and the PCBBiF layerthat was in contact with the light-emitting layer. The hole-transportlayer in the light-emitting element 3(B) included only the PCPPn layerthat was in contact with both the hole-injection layer and thelight-emitting layer.

Note that in an element emitting blue fluorescence, the HOMO level andthe LUMO level of a host material in a light-emitting layer are deep.Depending on the material for a hole-injection layer, the HOMO level ofa hole-transport layer often needs to be shallow so that electrons canbe extracted from the hole-injection layer. In that case, thehole-transport layer needs to have a structure in which a layer with ashallow HOMO level and a layer with a deep HOMO level are sequentiallystacked. Here, the mixed layer of PCPPn and a metal oxide was used asthe hole-injection layer in the light-emitting element 3(B). The use ofPCPPn with a deep HOMO level for the mixed layer allows thehole-transport layer to be formed using PCPPn with a deep HOMO level.Accordingly, even when the hole-transport layer has a single-layerstructure, holes can be injected into the light-emitting layer emittingblue fluorescence.

In each of the light-emitting element 1(R) and the light-emittingelement 2(G), the PCBBiF layer served as a layer for adjusting theoptical path length. PCBBiF has a shallower HOMO level than PCPPn. Thus,the power consumption of the light-emitting element 1(R) and thelight-emitting element 2(G) can be reduced. PCBBiF was also contained inthe light-emitting layers of the light-emitting element 1(R) and thelight-emitting element 2(G).

As described above, in the structure of this example, the light-emittingelements or a plurality of layers can use the same material, and thenumber of layers included in the light-emitting element can be reduced.It was suggested that the light-emitting elements with favorablecharacteristics can be manufactured at lower costs in a shorter processtime, and furthermore, a display panel with favorable characteristicscan be provided.

According to the above results, the use of the light-emitting elementsdescribed in this example can offer extremely wide-range colorreproducibility.

Example 2

In this example, the results of fabricating the display device of oneembodiment of the present invention are described.

<Display Panel>

First, the display panel used in the display device in this example isdescribed.

FIG. 27A is a schematic view of the display panel in this example. Thedisplay panel illustrated in FIG. 27A was an active matrix organic ELdisplay that had the light-emitting portion 250 with a size of 13.5inches diagonally, 1280×720 effective pixels, a resolution of 108 ppi,and an aperture ratio of 41.3%. The display panel included thedemultiplexer 253 serving as a source driver. In addition, the displaypanel also included the scan driver 255. Two sides of the light-emittingportion 250 were in contact with the region 251 transmitting visiblelight. The lead wiring 257 was provided along the other two sides.

A channel-etched transistor including a crystalline metal oxide in asemiconductor layer was used. An In—Ga—Zn-based oxide was used as themetal oxide.

Top-emission organic EL elements having a microcavity structure wereused as light-emitting elements. As a color display method, aside-by-side (SBS) method was employed in which light-emitting layersfor different colors are arranged side by side. The light-emittinglayers of the light-emitting elements were formed separately for eachcolor. Example 1 can be referred to for the details of the structures ofthe light-emitting elements for different colors. The area ratio withrespect to the BT.2020 color gamut was 106%.

FIG. 27B is a schematic view of a display device in which four displaypanels overlap with each other and are arranged in a 2×2 matrix. FIG.27C shows a schematic cross-sectional view taken along a dashed dottedline X-Y of the display device of FIG. 27B.

The display device in this example was formed by overlapping a pluralityof display panels so that a non-display region between display regionswas small. Specifically, the light-transmitting layer 103 was providedbetween the region 251 transmitting visible light of an upper displaypanel and the light-emitting portion 250 of a lower display panel.

A component blocking visible light such as a lead wiring or a driver wasnot provided at all from an end portion of the light-emitting portion250 to an end portion of the display panel along two sides of thedisplay panel, and the region along two sides served as the region 251transmitting visible light. The width of the region 251 transmittingvisible light of the display panel was approximately 5 mm. The thicknessT of the region 251 transmitting visible light (which can be regarded asthe thickness of one display panel) was very small, which was 100 μm orless. Therefore, although the display device in this example had aregion in which at most four display panels overlapped with each other,a step formed on the display surface side was extremely small; thus, aseam hardly stood out.

The four display panels had flexibility. For example, as illustrate inFIG. 27C, a region near an FPC 373 a of the lower display panel can bebent so that part of the lower display panel and part of the FPC 373 acan be placed under the light-emitting portion 250 of the upper displaypanel adjacent to the FPC 373 a. As a result, the FPC 373 a can beplaced without physical interference with the rear surface of the upperdisplay panel. In this way, another display panel can be provided onfour sides of the display panel, whereby a large-sized display device iseasily realized.

In this example, an attachment film including attachment layers on bothsurfaces of a base material was used as the light-transmitting layer103. With use of the attachment film, two display panels included in thedisplay device can be detachably attached to each other. An attachmentlayer on one side of the light-transmitting layer 103 was attached to asubstrate 211 a, and an attachment layer on the other side of thelight-transmitting layer 103 was attached to a substrate 201 b.

In FIG. 27B, the light-transmitting layer 103 includes not only aportion overlapping with the region 251 transmitting visible light, butalso a portion overlapping with the light-emitting portion 250. In FIG.27C, the light-transmitting layer 103 overlaps with the entire region251 transmitting visible light from an end portion of the substrate 201b, and also overlaps with part of the region 155 b including a displayelement. Note that the light-transmitting layer 103 is not provided on acurved portion of the display panel that is close to a portion to whichthe FPC 373 a is connected in FIG. 27C. However, the light-transmittinglayer 103 may be provided on a curved portion of the display paneldepending on the thickness or flexibility of the light-transmittinglayer 103.

Each of the display panels was formed by attaching a substrate and anelement layer with a bonding layer. For example, as illustrated in FIG.27C, a substrate 201 a, the substrate 211 a, the substrate 201 b, and asubstrate 211 b are attached to an element layer 153 a, the elementlayer 153 a, an element layer 153 b, and the element layer 153 b,respectively, with a bonding layer 157. As the substrates, highlyoptically isotropic films were used. The element layer 153 a has aregion 155 a including a display element and a region 156 a including awiring electrically connected to the display element. Similarly, theelement layer 153 b has the region 155 b including a display element anda region 156 b including a wiring electrically connected to the displayelement.

<<Display Device>>

FIG. 28 shows a photograph of an image displayed by an 81-inch diagonalmultidisplay. The multidisplay was manufactured by using 36 (6×6)display panels.

In this example, the display panels were driven by respective drivercircuits. A signal output from an 8K recorder was divided into 36 partsand input to respective driver circuits. The timing of scanning in thefirst stage of each display panel was set to be at the same time.

The multidisplay in FIG. 28 was a display device having a highresolution of 8K4K with 7690×4320 effective pixels. Note that the weightof one display panel including an FPC was approximately 26 g, and theweight of the 36 display panels was less than or equal to 1 kg (here,the weight of the display panel and an FPC is mentioned, and the weightof a frame for fixing the display panel, and the like is not included).

FIG. 29A illustrates a side view of the multidisplay. The display panel100 was attached to one plane of a support 376 (aluminum plate). Thesupport 376 had a curved surface whose curvature radius R was 5 mm, andthe display panel 100 was curved along the curved surface. The displaypanel 100 had a portion extending from the support 376. The portionoverlapped with an adjacent display panel 100. A driver circuit 375 wasscrewed on the other plane of the support 376. The display panel 100 waselectrically connected to the driver circuit 375 with the FPC 373.

The optical member 240 included the anti-reflection member 296, thesupport member 292, and the circularly polarizing plate 295. In thecircularly polarizing plate 295, a linear polarizing plate 295 a waspositioned on the viewer side and a quarter-wave plate 295 b waspositioned on the display panel 100 side. Here, the quarter-wave plate295 b overlapped with the linear polarizing plate 295 a to have an axisthat intersected an axis of the linear polarizing plate 295 a at 450.Therefore, in manufacturing a large-sized multidisplay, the circularlypolarizing plate 295 needs to be formed by using a plurality of thelinear polarizing plates 295 a or a plurality of the quarter-wave plates295 b. Here, the quarter-wave plate 295 b is thinner than the linearpolarizing plate 295 a and is seen through the linear polarizing plate295 a. Accordingly, a seam is less likely to be noticed in the casewhere a plurality of the quarter-wave plates 295 b are used than in thecase where a plurality of the linear polarizing plates 295 a are used.In this example, the circularly polarizing plate 295 was formed byattaching three quarter-wave plates 295 b to the linear polarizing plate295 a as illustrated in FIG. 29B.

The optical member 240 was screwed on a housing while the optical member240 was closely attached to the display panels. The optical member 240was not bonded to the display panels.

As described above, a large-sized display device capable of displayingan image with a wide color gamut was fabricated in this example.Furthermore, in this example, a display device in which an overlappingarea was less likely to be noticed was fabricated using a display panelutilizing a film that was highly optically isotropic and a circularlypolarizing plate. Specifically, the display device fabricated in thisexample had little reflection of surroundings. Furthermore, theoverlapping area was not obvious and was less likely to be noticed.Thus, the reflection of light from a surface of the display device wassuppressed.

REFERENCE NUMERALS

10: display device, 12: display device, 13: display region, 15: pillar,16: wall, 100: display panel, 100 a: display panel, 100 b: displaypanel, 100 c: display panel, 100 d: display panel, 101: display region,101 a: display region, 101 b: display region, 101 c: display region, 101d: display region, 102: region, 102 a: region, 102 b: region, 103:light-transmitting layer, 110: region transmitting visible light, 110 a:region transmitting visible light, 110 b: region transmitting visiblelight, 110 c: region transmitting visible light, 110 d: regiontransmitting visible light, 112 a: FPC, 112 b: FPC, 120: region blockingvisible light, 120 a: region blocking visible light, 120 b: regionblocking visible light, 120 c: region blocking visible light, 121: dummywiring, 123: FPC, 131: resin layer, 132: protective substrate, 133:resin layer, 134: protective substrate, 141: pixel, 142 a: wiring, 142b: wiring, 143 a: circuit, 143 b: circuit, 145: wiring, 151: substrate,152: substrate, 153 a: element layer, 153 b: element layer, 154: bondinglayer, 155 a: region, 155 b: region, 156 a: region, 156 b: region, 157:bonding layer, 201: substrate, 201 a: substrate, 201 b: substrate, 202a: substrate, 202 b: substrate, 203: bonding layer, 205: insulatinglayer, 208: insulating layer, 209: element layer, 211: substrate, 211 a:substrate, 211 b: substrate, 212 a: substrate, 212 b: substrate, 213:bonding layer, 215: insulating layer, 219: functional layer, 221:bonding layer, 223: connection terminal, 240: optical member, 250:light-emitting portion, 251: region transmitting visible light, 257:wiring, 261: substrate, 291: anti-reflection member, 292: supportmember, 293: anti-reflection member, 295: circularly polarizing plate,296: anti-reflection member, 300: touch panel, 301: transistor, 302:transistor, 303: transistor, 304: light-emitting element, 305:capacitor, 306: connection portion, 307: conductive layer, 308:connection portion, 309: connector, 310: input device, 311: gateinsulating layer, 312: insulating layer, 313: insulating layer, 314:insulating layer, 315: insulating layer, 316: spacer, 317: bondinglayer, 318: input device, 319: connector, 320: touch panel, 321:electrode, 322: EL layer, 323: electrode, 324: optical adjustment layer,325: coloring layer, 326: light-blocking layer, 331: electrode, 332:electrode, 333: electrode, 334: electrode, 341: wiring, 342: wiring,347: region, 348: region, 349: region, 350: FPC, 351: IC, 355:conductive layer, 370: display panel, 370A: display panel, 370B: displaypanel, 370C: display panel, 370D: display panel, 373: FPC, 373 a: FPC,374: IC, 375: driver circuit, 379: display panel, 381: display portion,382: driver circuit portion, 383: wiring, 387: crossing portion, 393:insulating layer, 395: insulating layer, 396: bonding layer, 1101: firstelectrode, 1102: second electrode, 1103: EL layer, 1103B: EL layer,1103G: EL layer, 1103R: EL layer, 1104B: color filter, 1104G: colorfilter, 1104R: color filter, 1105B: third light-emitting element, 1105G:second light-emitting element, 1105R: first light-emitting element,1106B: blue light, 1106G: green light, 1106R: red light, 1201: firstelectrode, 1202: second electrode, 1203: EL layer, 1203 a: EL layer,1203 b: EL layer, 1204: charge generation layer, 1211: hole-injectionlayer, 1211 a: hole-injection layer, 1211 b: hole-injection layer, 1212:hole-transport layer, 1212 a: hole-transport layer, 1212 b:hole-transport layer, 1213: light-emitting layer, 1213 a: light-emittinglayer, 1213 b: light-emitting layer, 1214: electron-transport layer,1214 a: electron-transport layer, 1214 b: electron-transport layer,1215: electron-injection layer, 1215 a: electron-injection layer, 1215b: electron-injection layer, 1301: substrate, 1302: FET, 1303B:light-emitting element, 1303G: light-emitting element, 1303R:light-emitting element, 1303W: light-emitting element, 1304: EL layer,1305: substrate, 1306B: color filter, 1306G: color filter, 1306R: colorfilter, 1316B: optical path length, 1316G: optical path length, 1316R:optical path length, 1307: first electrode, 1308: second electrode,1309: black layer, 1310G: conductive layer, 1310R: conductive layer,1900: substrate, 1901: first electrode, 1902: EL layer, 1903: secondelectrode, 1911: hole-injection layer, 1912: hole-transport layer, 1913:light-emitting layer, 1914: electron-transport layer, 1915:electron-injection layer, 7000: display portion, 7001: display portion,7100: mobile phone, 7101: housing, 7103: operation button, 7104:external connection port, 7105: speaker, 7106: microphone, 7200:television set, 7201: housing, 7203: stand, 7211: remote controller,7300: portable information terminal, 7301: housing, 7302: operationbutton, 7303: information, 7400: lighting device, 7401: stage, 7402:light-emitting portion, 7403: operation switch, 7500: portableinformation terminal, 7501: housing, 7502: display portion tab, 7503:operation button, 7600: portable information terminal, 7601: housing,7602: hinge, 7650: portable information terminal, 7651: non-displayportion, 7700: portable information terminal, 7701: housing, 7703 a:button, 7703 b: button, 7704 a: speaker, 7704 b: speaker, 7705: externalconnection port, 7706: microphone, 7709: battery, 7800: portableinformation terminal, 7801: band, 7802: input-output terminal, 7803:operation button, 7804: icon, 7805: battery.

This application is based on Japanese Patent Application Serial No.2016-233446 filed with Japan Patent Office on Nov. 30, 2016 and JapanesePatent Application Serial No. 2017-098884 filed with Japan Patent Officeon May 18, 2017, the entire contents of which are hereby incorporated byreference.

The invention claimed is:
 1. A display device comprising a first displaypanel and a second display panel, wherein the first display panelcomprises a first flexible substrate, wherein the second display panelcomprises a second flexible substrate, wherein the first flexiblesubstrate and the second flexible substrate overlap each other, whereinthe first display panel comprises a first light-emitting element, asecond light-emitting element, and a third light-emitting element,wherein light emitted from the first light-emitting element has a CIE1931 chromaticity coordinate x of greater than 0.680 and less than orequal to 0.720 and a CIE 1931 chromaticity coordinate y of greater thanor equal to 0.260 and less than or equal to 0.320, wherein light emittedfrom the second light-emitting element has a CIE 1931 chromaticitycoordinate x of greater than or equal to 0.130 and less than or equal to0.250 and a CIE 1931 chromaticity coordinate y of greater than 0.710 andless than or equal to 0.810, and wherein light emitted from the thirdlight-emitting element has a CIE 1931 chromaticity coordinate x ofgreater than or equal to 0.120 and less than or equal to 0.170 and a CIE1931 chromaticity coordinate y of greater than or equal to 0.020 andless than 0.060.
 2. The display device according to claim 1, wherein thefirst light-emitting element, the second light-emitting element, and thethird light-emitting element comprise an electron-transport layerbetween a pair of electrodes and each comprise a light-emitting layerbetween the pair of electrodes, wherein the light-emitting layer in thefirst light-emitting element, the light-emitting layer in the secondlight-emitting element, and the light-emitting layer in the thirdlight-emitting element are separated from each other, and wherein thefirst light-emitting element, the second light-emitting element, and thethird light-emitting element share the same electron-transport layer. 3.The display device according to claim 2, wherein the firstlight-emitting element, the second light-emitting element, and the thirdlight-emitting element comprise a hole-injection layer between the pairof electrodes, and wherein the first light-emitting element, the secondlight-emitting element, and the third light-emitting element share thesame hole-injection layer.
 4. The display device according to claim 2,wherein the first light-emitting element, the second light-emittingelement, and the third light-emitting element each comprise ahole-transport layer between the pair of electrodes, and wherein thehole-transport layer in the first light-emitting element, thehole-transport layer in the second light-emitting element, and thehole-transport layer in the third light-emitting element are separatedfrom each other.
 5. The display device according to claim 2, wherein thefirst light-emitting element, the second light-emitting element, and thethird light-emitting element each comprise a reflective electrode and atransflective electrode as the pair of electrodes.
 6. The display deviceaccording to claim 1, wherein one or both of the first display panel andthe second display panel comprise a curved surface.
 7. The displaydevice according to claim 6, wherein the radius of curvature of thefirst curved surface is larger than the radius of curvature of thesecond curved surface and is less than or equal to 10000 mm, and whereinthe radius of curvature of the second curved surface is greater than orequal to 1 mm and less than or equal to 100 mm.
 8. The display deviceaccording to claim 1, wherein the first display panel comprises a firstcurved surface and a second curved surface, wherein a radius ofcurvature of the first curved surface is larger than a radius ofcurvature of the second curved surface, wherein the first curved surfacecomprises a first display region, and wherein the second curved surfacedoes not comprise the first display region.
 9. The display deviceaccording to claim 1, further comprising a first module and a secondmodule, wherein the first module comprises the first display panel andat least one of a connector and an integrated circuit, and wherein thesecond module comprises the second display panel and at least one of aconnector and an integrated circuit.
 10. An electronic devicecomprising: the display device according to claim 1, and at least one ofan antenna, a battery, a housing, a camera, a speaker, a microphone, andan operation button.
 11. A display device comprising a first displaypanel and a second display panel, wherein the first display panelcomprises a first flexible substrate, wherein the second display panelcomprises a second flexible substrate, wherein the first flexiblesubstrate and the second flexible substrate overlap each other, whereinthe first display panel comprises a first light-emitting element, asecond light-emitting element, a third light-emitting element, a firstcoloring layer, a second coloring layer, and a third coloring layer,wherein the first light-emitting element and the first coloring layeroverlap each other, wherein the second light-emitting element and thesecond coloring layer overlap each other, wherein the thirdlight-emitting element and the third coloring layer overlap each other,wherein light extracted through the first coloring layer has a CIE 1931chromaticity coordinate x of greater than 0.680 and less than or equalto 0.720 and a CIE 1931 chromaticity coordinate y of greater than orequal to 0.260 and less than or equal to 0.320, wherein light extractedthrough the second coloring layer has a CIE 1931 chromaticity coordinatex of greater than or equal to 0.130 and less than or equal to 0.250 anda CIE 1931 chromaticity coordinate y of greater than 0.710 and less thanor equal to 0.810, and wherein light extracted through the thirdcoloring layer has a CIE 1931 chromaticity coordinate x of greater thanor equal to 0.120 and less than or equal to 0.170 and a CIE 1931chromaticity coordinate y of greater than or equal to 0.020 and lessthan 0.060.
 12. The display device according to claim 11, wherein thefirst light-emitting element, the second light-emitting element, and thethird light-emitting element comprise an electron-transport layerbetween a pair of electrodes and each comprise a light-emitting layerbetween the pair of electrodes, wherein the light-emitting layer in thefirst light-emitting element, the light-emitting layer in the secondlight-emitting element, and the light-emitting layer in the thirdlight-emitting element are separated from each other, and wherein thefirst light-emitting element, the second light-emitting element, and thethird light-emitting element share the same electron-transport layer.13. The display device according to claim 12, wherein the firstlight-emitting element, the second light-emitting element, and the thirdlight-emitting element comprise a hole-injection layer between the pairof electrodes, and wherein the first light-emitting element, the secondlight-emitting element, and the third light-emitting element share thesame hole-injection layer.
 14. The display device according to claim 12,wherein the first light-emitting element, the second light-emittingelement, and the third light-emitting element each comprise ahole-transport layer between the pair of electrodes, and wherein thehole-transport layer in the first light-emitting element, thehole-transport layer in the second light-emitting element, and thehole-transport layer in the third light-emitting element are separatedfrom each other.
 15. The display device according to claim 12, whereinthe first light-emitting element, the second light-emitting element, andthe third light-emitting element each comprise a reflective electrodeand a transflective electrode as the pair of electrodes.
 16. The displaydevice according to claim 11, wherein one or both of the first displaypanel and the second display panel comprise a curved surface.
 17. Thedisplay device according to claim 16, wherein the radius of curvature ofthe first curved surface is larger than the radius of curvature of thesecond curved surface and is less than or equal to 10000 mm, and whereinthe radius of curvature of the second curved surface is greater than orequal to 1 mm and less than or equal to 100 mm.
 18. The display deviceaccording to claim 11, wherein the first display panel comprises a firstcurved surface and a second curved surface, wherein a radius ofcurvature of the first curved surface is larger than a radius ofcurvature of the second curved surface, wherein the first curved surfacecomprises a first display region, and wherein the second curved surfacedoes not comprise the first display region.
 19. The display deviceaccording to claim 11, further comprising a first module and a secondmodule, wherein the first module comprises the first display panel andat least one of a connector and an integrated circuit, and wherein thesecond module comprises the second display panel and at least one of aconnector and an integrated circuit.
 20. An electronic devicecomprising: the display device according to claim 11, and at least oneof an antenna, a battery, a housing, a camera, a speaker, a microphone,and an operation button.